Of all the modifications you can do to your TPI motors porting the plenum is one of the best but it is one you have to do your self. If you don't have the tools and/or the facilities to do it, well you can spend a lot of time and money and still have it being far from the quality of the plenums I sell. Nobody markets and aftermarket plenum but they should. The stock plenum was designed to feed the chevy 305 motor. When used on the 350 motor the runner size is barely adequate. When you modify your motor with things like an aftermarket base or a set of runners you need to open up the plenum to take full advantage. If you don't your losing horsepower! If you've gone as far as to go with a cam or a set of better heads you can expect BIG gains when you change to one of my plenums.
Attention! I have just had one of my plenums featured in Car Craft and have had my plenums in GM High Tech Performance magazine. I have ramped up my production. All plenums are now C-N-C Ported on a 3-axis milling machine. I will begin advertising in 2 to 4 magazines starting in about a month's time. Look for me in Corvette Enthusiast, Vette, Corvette magazine or GM HighTech Performance. I have not decided on the exact publications yet. I expect to be swamped with work. I will also try to do 2 corvette shows a year. Most likely Corvettes at Carslile and perhaps Bowling Green. L