my ECU is throwing out MAF circuit malfunction code and IAC-v codes. my engine has lost compression and power tremendously. What is causing it?? because i was told that if the MAF is out, the rpms wouldn't go past 2500. my car revs all the the way to 7k but it is just a little hesitant. sometimes it refuse to down shift also, unless i floor it completely? what is causing this???? is it the MAF and IACV or could it be something else????? ive already replaced the knock sensor and i use premium fuel. my mods are warpspeed y pipe catback exhaust and obx intake.

 

Sounds like a bad knock sensor to meeeeeeeee :-x
Do you have an 0304 code at all?
Is there slight pauses in acceleration when you floor it? No torque down low?
Then its a knock sensor