Steve replied:

i would check all mounting bolts nuts clamps any insulating bushes, also check snorkel where it goes into fender, could be rubbing on guard, snorkel isnt damaged ie cracked.
there isnt any restrictions in the intake system, i have had that one before somebody had played a practical joke on someone by taping up half the air cleaner but had put it back in upside down and the engine couldnt suck any air so you could imagine the damage to all the plastic intake bits