Ok I have a built l61 2.2 on 18-20 psi boost on e85 I have bin recently running great till i got a tune up from my budys shop fix all vac/boost leaks it was with iridium plugs 2 steps colder gapped to .27 for over a year I recently swapped a LSJ THrottle body now I'm getting bad spark blowout in lower gears 1-3rd gear at lower boost pressures 4-7 psi it breaks up pretty bad then kicks back in higher boost I swapped some 2 step colder vpower plugs gapped to .26 same thing gonna swap them again tomorrow with less tight gap what els could be the issue??!

 

Go back to your other TB and see if it still does it.

 

My old throttle body was just cutting out at 4500 or 5psi wouldn't go past now it's better but completely fixed the issue