i have had my 1jz for about 8 years. same stock turbos not blown, same blitz exhaust, and intake. i just recently did a tune up with new plugs and oils and also added a 3' downpipe and eliminated the cat. since i installed the downpipe, it seems like when i try to floor it the car sputters. rather it be in 1st or 5th i get the sputter. can anyone let me know what is going on?

What's your boost at WOT. You might be hitting boost cut with the 3" DP.

no guages in the car so i have no clue. but if that is the case does the afc take care of that?

You need a boost controller, fcc or bcc. By freeing up your exhaust with the DP you in turn raised boost pressure

Either what LexusFTW has said or lower the gap of the spark plug from 1.1mm to 1.0mm then 0.9mm then 0.8mm (NO LOWER) until it stops missing at WOT.

Its a common fix because when you are chasing dyno numbers the first thing that needs upgrading is the ign coils.

i have hks iridium spark plugs. i will try gaping the old plugs that were in there to see if it works