Where is and how to change the airfilter - 2003 Triumph Speed Four

Take it back to him and leave it for him to sort it out

spark plugs and wires and fuelfiter and airfilter if airfilter is drity

Those hoses are probably crankcase ventilators. It allows crankcase pressure and vapors to be vented and sent back to the combustion chamber. If you eliminated them, pressure could build up in the crankcase and cause issues with smooth running.

Not Idling there are multiple reasons not only carb.
1, Improper Timming 2, Compression leak 3, Bad spark-plug 4, chocked Airfilter.
clean the spark plug and check the firing clean or replace airfilter check timing check for leaking gasket in cylinder and cylinder head check valve seal check all these as I mentioned order it will help.

change gas cap, check bad 02 sensors

if it's simialr to my mazda...there's a push-in clip and a retractable cord that support the glove box. Detach the cord and push in the clip and it should drop down and slide out.
The filter should be behind a clip-on compartment door.

It is. I believe on your MDX you have to remove the glovebox 10mm screws. Then there is a drawer in the plastic HVAC housing that unclips on both sides and slides out. If it hasn't been changed before, on most Honda and Acura SUVs you have to carefully cut the plastic that covers the support to remove the metal bar to get to the drawer. You need to keep the plastic because it screw into it's old position after the job is complete.

There should be two Torx 25 screws on the airbox facing up right in the center.

Unscrew those two, but don't go so far to totally remove them, they are supposed to stay in with the filter cartridge and the filter element is right in there.

go to a near garage and ask him to open the socket and put a air filter and its located in the bonet and take care that its a petrol car