11. So if I am making the same boost pressure, why does it matter if its leaking a little?
--Because even if you are hitting target boost, your turbo is having to work harder to get there. A harder working turbo produces a hotter air charge, as its higher in its efficiency range (or worse, completely out of it). This means less dense, which will produce less energy when ignited. This also means higher chance of detonation, which even if its very light, will result in your ECU pulling timing. Also bad. Lastly, hotter air in=hotter air out. Higher EGTs. Even if only slightly.