my car pulls harder at 1/2 throttle than full throttle, when i put my foot to the floor my car feels like its slowing down, what can I check?

Usually this comes from a restriction of some sort.

Either an air intake problem, a fuel delivery problem, a restricted exhaust/cat problem, etc.

Is the clutch slipping?

What have you checked already?

I have also noticed those symptoms from a boost leak. Do a boost leak check on it and see what happens.

I have checked all the sensors on the throttle body except the IAC, Friday i'm going to check fuel pressure, injector resistance, and do a boost leak test, remember I don't have a catalytic converter so no issues there. and I also have Upper intercooler piping with a Greddy type S BOV so i wouldn't expect it to leak there but who knows? any more tips??

list more mods.

Mine acted like this sometimes when my ignition timing was way off. Grab a light gun and check your timing. You should be around 5 degrees BTDC.

id think a restriction around or in the turbo. Is your turbo being properly cooled? id think it would bog down if it got hot enough and if its getting hot enough, your prolly just destroying it. Um... boost leaks are possible.. are you saying half throttle in the boost? or what cuz if your saying you are getting this problem in the boost then yea, check for boost leaks and check your fins on the turbine n all that. Then again.. we need to know more? Are you getting misfires? Is your cam angle sensor properly held down.. hmm yea

List your mods. Do not say "remember" to anyone when you didn't tell us. What boost are you running? Too much boost = pulled timing = slow car.