I was talking to a buddy who is pretty into 3D printing (and has printed various things for automotive applications) and he claimed that there was a readily available "automotive ABS" that could be used to print an intake and would easily stand up to the heat, vibration, fuel, etc. as it is the same material a lot of OEMs use for their intakes. He did mention it took a printer capable of higher temps but I found it intriguing...
I have the ported exhaust, "Dawg Style" UIM, relieved y-pipe, hi-flow cat, Hypertech chip and a 57MM throttlebody. Basically all the breathing mods. Each one added a little to the performance but then I did the 1.6 rockers and WOW! what a difference.
I consider the rocker mod to be the one that brought all the pieces together, giving me a very nicely balanced car which also looks completely stock.
As for the RMP power limit, I can say unequivocally that the rockers made a huge difference. Where the stock car ran out of breath at about 4500RPM's, the modded car easily pulls all the way to 5500RPM's and there still some left but that's as far as I want to push a 30 year old engine even if it only has 60K miles on it. In fact, being an automatic I have to manually shift because the factory shift point is way too low for the modded engine.
As far as I am aware my engine is stock but it pulls super hard to 5500