will a one intake intake spacer eliminate the "choking" effect of a stock intake above 4500 rpm? if so what other modifications are needed, egr etc....
no...the stock intake is just made restrictive thats all there is to it. In order to fix that you either have to have it ported out or do what I did and throw out that POS and get an aftermarket intake.
By adding a spacer you are lengthening the runners which will make it even worse. Just remember, a general rule of thumb is that the shorter the runner length, the higher up in the rpm range the intake will make power. The only way to fix it is to shorten the runner length (you may be able to mill a little of the upper and lower intake were they meet) or swap it for somehting better like an edelbrock.
By adding a spacer you are lengthening the runners which will make it even worse. Just remember, a general rule of thumb is that the shorter the runner length, the higher up in the rpm range the intake will make power. The only way to fix it is to shorten the runner length (you may be able to mill a little of the upper and lower intake were they meet) or swap it for somehting better like an edelbrock.
Paul is right....best bet if you wanna keep the stock intake is send it to TMOSS....he has gotten solid results with ported stockers....im gonna agree with Paul and reccomend the edelbrock but its up to you really