I am trying to diagnose what the problem is with my car now. Over the weekend I swaped the S5 intake manifolds on to my 87 S4. I thought that this was going to be the greatest power adder that I would ever do to my car. I am saddly dissapointed. The new setup feels much slower that the original manifolds that were on the car. I dont have the VDI hooked up b/c I dont have the air pump anymore. So I am in the process of using a low psi system with and RPM activated switch to open the VDI system up. But, the car feels pretty good down low, and then when it hits 4500, the power kinda falls off. I know that the VDI will help, but even up to that point, the car feels slower than with the S4 manifolds. Could I have a vacuum hose hooked up to the wrong spot? I have two vacuum hose lines bridged together that run to the top manifold, and I am going to split them apart so they each have their own line. But other than that, I dont know what else could be wrong. If you can help out please do. I am going to the track tonight to see what the numbers are. Thanks.

The s5 manifold makes the same power as s4 below 6k rpm. The graphs are nearly identical, just with the s5 peaking at a higher rpm.



And yes, the VDI not being operable will make a big difference in top end. But its still not a big gain, its around 10 hp more than s4.

10 rwhp or 10 bhp?