i fitted a P75 TB on my old sei 1.1, just take the top off the 75 TB and fit the fit the 1.1 TB top with injector onto it but dont forget the P75 stack that fits under TB as this is matched to the it , i think this will give you 38mm it worked well on mine, but i had done cat back exhaust,air filter and the P75 TB all in one go so i cant really tell you the individual benefits, but it all made a good upgrade