It isn't to make gains on the n/a engine as such, its to get the bay ready for na-t. I much prefer how the intercooler plumbing looks with the tt inlet as apposed to the pipes being stretched right across the bay. Do you mean an itb set-up? I looked into that and it was very expensive for very small gains.
A tt conversion was on the cards but price wise it's a world away from going na-t, i also am looking to keep an n/a engine also because they are much cheaper to maintain or replace should something go wrong. Par mapping, which im waiting for a quote back for, the cost of na-t is coming in at nearly 900 less than a low mile tt lump.