1999 Chevy Tahoe

I have a 99 Chevy Tahoe that has a problem when you floor it, it rev's to the rev limit when you ease the gas in park but the second you get past 50 percent throttle it sounds like it's choking and the rev drops to 3000, i've changed spark plugs, cap, rotor, air filter, cleaned the MAF sensor, changed all 4 O2 sensors, and boths cats. I've been told that since I have the spider style injectors that there could be a crack in one of the plastic tubes that feeds fuel to the cylinders. I've also read online that the problem could also be the fuel pressure regulator.