MY KC drop in is awesome, I imagine the prototypes are better based on what I've read on fte as 06h3 mentioned. I could def. handle some 160/30's but dont want to drop the $ on a tranny right now...
For stock injectors the kc balanced assembly is great (or stock plus drop in same thing)
Keep your stock exhaust, its stainless, well engineered and will hold up best, no need for larger size, just delete muffler and straight pipe with no worry of drone, or put straight thru muffler and it wont be much louder than stock. If my Truck did not come with the gay ass banks monster 4" already i would still be rocking the stock like i did with my 03'