Sheesh, doesn't anyone on this thread have my book? The data from 2500-3000 is all in there, Performer vs Performer RPM. On my 410 HP 428CJ, the Performer makes torque of 389 to 438 lb-ft from 2500 to 3000 RPM, and the Performer RPM makes torque of 340 to 406 lb-ft. On this engine the Performer is better in this range, and is actually better than the RPM up to 3500 before the RPM takes over and makes a lot more power. Both intakes peak at nearly the same torque, 485 lb-ft around 3500 RPM.
On my 500 HP 390 stroker engine, I only tested from 3000 RPM up, but basically the two manifolds behaved the same as the other engine from 3000-3500. But on that engine the RPM made more peak torque, and caught up with the Performer a little sooner.
I have heard a lot of anecdotal evidence that the Performer RPM is better than the Performer 390 at all engine speeds, but it is all based on the "seat of the pants" dyno, not actual data. I'll stand by the back-to-back test data in my book, and say that the Performer 390 is better than the Performer RPM up to around 3500 RPM.
I love your book and reference it regularly, but IMHO, and honestly with all the peer respect anyone in the world could muster...it's testing is far from this target. WOT dyno runs on smaller engines with curve analysis,
I think, just doesn't match the part throttle and mileage discussion. I really don't know, nor does anyone really know how throttle jockey movements will respond between the two. For me, on a small motor, 390 with 270H and a 600, the Performer 390 was pitiful and a PI and a unmachined SD were both nice to drive.
That being said, in the end, he is looking for seat of the pants and mileage, so I don't see any reason other than buying and fitting a manifold not to do it, but I cannot imagine it's the right thing
We do have a big inch engine that did exactly this, Turbohunter's truck. Marc ran a stroker with a Performer and the world didn't end, but on the other end of the spectrum I run a Victor on my 462 and it makes tons of torque, and got 14 mpg with a 3310 before the fuel injection.
I'll admit it's not scientific, but I do think it's going to lose enough power that it will be less effective through each shift. I say go for it if he wants to try it