Like most of you know i own 2 si...so i usualy pass time comparing them. One of them is a pure si and revs great and sounds great.

The other one has a japanese engine a mpfi d15b with the head is from a 89-91 sohc head not the vtec one but its not carburated.. it has mpfi on it...so guess the previous owner just put pulled out the a6 and put a crappy used to be carburated block.

The only problem is that when I rev higher then 3000 its starts to do a whinning noise like if it was supercharged...which is not the case...i tought it was the bearings on the ac compressor (which never conditionned the air). So i pulled out the belt and also the tensionner by mistake...and that noise was still there. so i opened the hood and let the engine run and press the trotle...and the noise seemed to come from the head( i guess the air is restricted over that amount of rpm)...with that in mind. the probability that its the carburated is high.

to conclude..Is it a good thing...or a bad thing ...how far can i push it before it really over revs...