You can say they are next to impossible but you don't know the shop the tuner or what he is capable of, tuning makes all the difference. You may have seen the post on here with a vortec sc and a methanol system on a bone stock engine no other mods and it put down 407 hp to the wheels that was tuned by the same person, Ravi at Speed Freaks.
Sure, that's on an FI engine, and where he can add a hell of a lot more timing due to the methanol.
But your car, for all intensive purposes, is bone stock. Let's examine it for a minute:
FIPK, maybe 4HP and that's generous
Prochamber and midpipe, maybe 10 HP.
Flowmasters, most likely none.
So in essence, you gained about 15 HP (generous) over a stock GT. Let's say stock you dyno about 235, so you mods give you a total of 250, again generous. Now, are you saying by "tuning" your car you netted another 26.3HP? There are cars on here with stage 1 cams, LT's, full exhaust and TUNED that are making that HP level, and you're telling us that you did the same with only an intake and semi-exhaust?
Think about that for a minute, and you'll see why many people are disputing what you're posting on here.