My 2010 rmz 450 crackles and pops at low revs, and surging when cruising, also backfires when i shut of the throttle, i have fitted a wiseco fuel mangement unit and played around with it but no luck,

It sounds like you have a problem with fuel starvation. Check from fuel tank to carburetor. Tank may have sludge in it, shut off valve may have clog or rust, fuel lines when old tend to collapse in on them selves, filters clog or become dirty, and carburetors tend to accumulate dirt, water, clogs, and may need to be rebuilt. Since you are running fairly well, your problem may be small and inexpensive. GOOD LUCK FRIEND.

Maybe your throttle slider is jammed open or u were running out of fuel or the throttle cable jumped out of its housing from the top of the carb.

Sounds like a timing issue or simply bD spark plugs. Do a spark check and see if you have a kice blue arc on the plugs. Also I've seen the flywheel key break on those before. That situation will greatly affect the timing Nd cause back firing also check your valve clearance.

http://media.suzukicycles.com/~/media/PressKits/2010%20RMX450Z%20Launch.ashx

Try putting fuel injector cleaner along with 93 octane fuel

clean carb and tank

Could be contaminated fuel, or bad spark plugs.

Crackling and backfire is nearly always lean on fuel condition...
open your air fuel mix screw tiny amount at a time and test to see if helping this should clear up the popping..
Please note if you need to open the air fuel mix screw more than 3 full turns from fully closed then the easiest solution is leave the air fuel screw at 2 turns out from closed and increase the size of your pilot jet by one or two sizes.. they very cheap to buy few dollars each.
I would suggest if your only popping and crackling a little then small adjustment on the air fuel mix screw will cure it for sure
Being YZ I find an occasional pop or backfire when de acelorating is exactly how they should be if you don't get a pop or crackle every now and again then chances are it running to rich.
but if it is regular occurance then definitely needs fine tuning or larger pilot jet installed
good luck regards Jamie

i have that bike i am 6ft and 165 lbs the bike is awesome i love it, i have it the softest it can be and its still not a soft ride to just sit and cruise around on the bush tracks. the 4 speed gear box is alright makes going up tuff rutty hills hard but hold on and keep the throttle on and it will go. bike pulls in any rev range even when iv doubled someone so it has the torque
best of luck

You need to most likely have the TPS checked (set at full throttle not running 4.85 volts) and or CDI remaped at dealer