Good point. I have.
A local guy had a MOTEC EFI conversion done......with the stock manifold. He was disappointed in the results. 420 RWHP I believe was the max which is right about 500 FWHP. I don't recall the head work/porting etc that was done.
Realize that this by itself is not a damnation nor approval of a stock manifold, but rather a potential showing of the limitations that a stock manifold will produce - when this engine was compared to a nearly identical engine with a Carrera manifold.
I believe the Carrera manifolded engine had another 40hp.
YMMV, take this for what it is.
3.4L, SC heads, 964 cams, B&B headers, K27 HF ZC turbo, Ruf IC. WUR & RPM switch, IA fuel head, Zork, G50/50 5 speed. 438 RWHP / 413 RWTQ -
"930 is the wild slut you sleep with who tries to kill you every time you "get it on" - Quote by Gabe
Movie: 930 on the dyno