ohh and I have a little experiment for ya, in regards to that rubber IC pipe VS aluminum.
If they are the same inside dia, or damn close… take zip ties, one per 1/4 inch, and wrap them up tight around the stock rubber charge pipe, snug them so they dont really move around by hand, but not so tight it crimps the tube. cover it start to finish. now go drive it and see if it boosts differently.
If my hunch is correct, its expanding the stock tube under boost, and the aluminum one wont. Again, less volume (aluminum tube with say 300CC of volume, vs a rubber one 300cc at rest and 400cc puffed out under boost) = more pressure. So another words, since the boost and wastegate didnt change, the turbo can “overboost” because it has less volume to fill (in less time too).
this is also seen on a much bigger scale when someone goes from 3" charge pipeing to 2.25" charge piping on the exact same turbo configuration, IE no other changes made. Just yours is on a smaller scale because the % of change in the system was made.
You’re absolutely right. The stock IC pipe is a fabric contruction and it definitely “balloons” under boost. With the hard pipe you can feel the power delivery being a lot smoother throughout the band.