Just a quick question because i am stupid

Having a wee bit of bother with the Escort GTi i have currently. Changed the Idle Speed Control Valve which has cured idling issues the car had, but i have noticed the car pinking and hitting dead spots basically and just no power when i give it a bit (seems to be about 4000 revs or thereabouts) The car as far as i know only has 1 mod and that's 2-litre cams rather than the standard 1.8 cams (although i do have the standard cams in the garage). Just wondering if the Air Flow meter in the car could be causing problems due to different cams and slight power increase. I was told to perhaps change to a 2-litre air flow meter and throttle body but i don't know if that'll help. Could the Air Flow Meter be faulty? Not sure how the air flow meter works with modifications to the car - would it have to be changed or removed at all?

Any ideas at all guys? Perhaps fuel pressure could be low also? Don't have time to get the car in anywhere this week so just looking for a few ideas first.

Cheers peoples