If you change from a 2.0 outlet to a 2.5 pipe, you're going to get abrupt changes in air flow and create a vortex and dead air spots. Most companies use 2.0 and transition up to the size of the TB... like HRC. It from 2.0, to 2 1/8, to a final 2.25 to the TB. Small changes create a cleaner flow path and less wasted energy. Most times it isn't enough to even care about, so going from a 2.0 to 2.25 or 2.5 transition on the compressor outlet is nothing uncommon. The V6 kit we produce uses a kick from 2 to 2.250, no problems thus far and It generally acts like a reversion hump when the throttle closes at low boost when compressor surge is most likely to happen. Works out pretty well.

I'd leave it. It's not going to change much like if you were to swap the manifold piping diameter or downpipe sizing.

Exile Racing Technologies, Inc.