Bike has cobra pipes,backfires when I let off gas,lot of popping when running steady speed.

The metal they are made of shouldn't make that much difference. It tends to be a trade off between them. Copper tops produce a better spark but they commonly only last about 20 to 30 thousand miles between changes.
Irridium plugs last a lot longer but they don't produce as good a spark.
Your problem sounds like it could be a fuelling issue. Back firing is usually a sign of a wrong fuel to air mixture. Too much or too little fuel in the mixture. Too much fuel ignites in the exhaust at the wrong moment causing a 'bang' out of the tail pipe.
When was it last given a Full Service? You could try running some Good Quality fuel injector cleaner through it.
Try this. At about half tank add the correct amount of Fuel Injector Cleaner to the tank and just let the bike idle. DON'T Rev it up as this weakens the amount of cleaner going through the engine. Let it idle for about 10 minutes to get the engine to working temperature. Take it out for a good long ride at a constant steady speed, (A freeway ride). Don't race the engine to high speeds. Let the tank run to almost empty then fill to the top with one more dose of injector cleaner. Use the bike as normal for that tank full then fill with just fuel as normal.
If this doesn't help get a Good Bike mechanic to listen to it. The actual sound can be a clue. Backfiring can also be confused with 'Popping and Banging'. That's that spitting and banging noise performance cars make when they let off the gas quickly after accelerating really hard.

Backfiring is caused by a lean air/fuel (A/F) ratio. A leaner A/F ratio takes longer to burn and will continue to burn in the exhaust, hence the backfiring. Is the bike stock, or have you changed the air cleaner or pipes? Both of these changes will result in a leaner A/F ratio. HD bikes with fuel injection already run lean to meet emissions requirements, so changing pipes, etc. will make the problem worse. If you have not made any changes to the bike, make sure that the fuel system is clean and you are using good quality gas. You can also have the bike's computer (ECU) remapped to run a little richer. Your dealer may be able to do this for you, or there are aftermarket ECU tuners available for your bike that can adjust the fuel map and ignition. These will give you the added benefit of more power and a cooler running engine.

hi the air box and exhaust restrict the air movement through the cyclinders to match the jets in the carbs. i have bikes that you can remove baffles or airbox with no problem, others are so finely tunes that it is impossible to run the bike without the restriction. the easy option would be to get a jet and air filter kit. then if you need to restrict air flow any (hopefully you wont need to) you could very slightly raise the inlet/outlet valve gaps to the maximum amount which will open the valves for a slightly shorter time. you could also restrict the exhaust by using large washers on the exhaust gaskets. similar to those used to restrict a bike.

I do not agree your bike should run better then it sounds like it is. Just throwing on a set of pipes and a carb kit is not always all that needs done. I ask about the air filter because it seems your motor is getting to much gas and not enough air. The thing I would do next is to get a higher flow of air on the intake side by going to a high flow air filter. A quick check to see if this will help is to temporarily remove the air filter and test ride the bike. If it runs better without the filter this tells you a high flow filter will help. Your bike may need more work than this to get it right on. The other thing you could have done is get someone to jet in the carb to cut down the fuel flow and get the fuel air ratio right on.

I have the same bike with 8000 miles on it., Alot of bikes backfire especially these with the emissions package. I'm a smog tech and what backfiring means is detanation from a lean condition. The cylinder gets hot on decel and you get the pop. You could go the sabrehood forums and register and talk to people about these bikes.

What I did was put a k/n filter. put a stage 2 jet kit and a cobra slash cut exhaust and this seemed to reduce the amount of backfireing alot.
Bikes loud and maybe a little quietier exhaust would of been better but for now bike runs alot better.
Hope this helps

Your bike is running lean (too much air and not enough fuel). What, if any, modifications have you done to the bike? If you changed the exhaust out for louder pipes, you need to adjust the f/a (fuel/air) mixture in the carburetor to compensate for more air going through the bike. Let me know here if you have made any type of mods to the bike.

If the bike is fuel injected, the module should fix it. If the bike is carbureted, you don't need the module but you will need to re-jet the carb to enrich the mix.

Sounds like the carb has not been cleaned properly, gas overflow like that could be caused from a worn seat/needle. Did you put after market exhaust on it?

Check valve clearance, as vlaves wear the gap closes, most riders don't bother to adjust them till they have a problem like this.... By the way the valve may be part of the issue for backfiring while deccerating but Pipes cause this.

I am not sure what you mean on the "running fast" statement. If idle speed then turn the idle screw outward to slow down the idle.

The backfire is caused by turning off the ignition key when the bike is at high revs. let it idle down THEN turn it off. The backfire is there because the carb idle circuit is active anytime the piston is in motion. Gas goes into the cylinder as the bike revs down then a hot spot in the exhaust pipe finally ignites the built up gas. There is your backfire.

Is the running fast question answered? Give me more information on the problem if it isn't.

Please rate this answer. Thanks njv6!