Mods on this "high end" engine are f'ing frustrating as the two or three that know anything don't want to share, and i guess i can't really blame them. Since they are not likely to speak up, i'll give my gut feelings. And i'm sure there are some comptech NA engine guys here that will provide better info perhaps negating my comments, and of course i welcome that. The factory heads flow enough for standard displacement engines and possibly even the strokers. Headwork normally simply takes advantage of poor flowing heads which we likely don't have. Generally porting and larger valves simply trade mid range HP for high end HP making the engine peakier. While i like this for the street, it doens't make the car much faster as you are just trading power from one range to the other. It then depends on the gear ratios as to where you want the power. From my experience it's the racers that know what will help and not a flow bench technition. Bottom line, SHAD, SHAD, SHAD is likely the only one who knows about head flow regarding NA, although his input will be all memory as i doubt he's done hardly any NA's in the last decade. But he was around when HONDA was bulding high output NA engines. The spice car put out 440 crank although that engine probably would have too little torque for our full size sleds. I've been out of the community for many years, so if i'm disregarding others out there please accept my apologies in advance. You could help us out! It's so frustrating coming from the iron v8 world were folks will share almost everything all the time. The perception of high end money chasing these high end cars creates opportunitys that screw the DIY guy. And of course if you don't know what your tuners mods are, you can't really tell if you are getting your moneys worth, as well as repairing your ride down the road. It's kept me from major mods for many years. Things ARE much better than they used to be though. I'm on the same track as you. We'll get there.