My neighbor had and irocz with the tpi engine. All he did was a cam and exhaust and that thing was definitely no slouch. For the average build it's a good setup and performs well. Plus it's very street friendly especially as a daily driver or such. Now if you were trying to put 500 to the wheels i can see that it will be a problem. But to get 400 crank hp shouldn't be a problem at all. Just like carburetors it will only support so much power. You can run a mild small block on a 600cfm but you'd definitely need to step up to a larger carb if you wanted more power. Same with the tpi. The stock setup can handle moderate power but it needs to be modified to make support higher power levels.
Saying the tpi sucks because it can't handle high hp is like saying tbi sucks for the same reason. Or that 2barrels suck cause they can't make 6million horsepower. Everything has it's purpose and the tpi does exactly what it was designed to do.