I dont have a thread for my current car, its an ED low boost kit, there is an intensive build thread on my previous 260 bhp ph1 turbo ill have to try and find if youre interested, it was an unorthodox conversion however it had a stock bottom end which was an old tired 120k mile bottom end and was obviously a lot older being a phase 1, and im pretty sure the original owner had no mechanical sympathy either as the car was bought with a snapped cambelt, and it took that 330 bhp before the conrod bent.
There has been others, like T.Trophy who ran 300 bhp on a stock bottom end for a fair while before he forged it and went 500 bhp, so what im saying is, you could take the ED low boost conversion and add the additional price of a megane headgasket and just run enough boost to make 250-300bhp, the meganes F4RT's handle it fine, and there is minimal differences between engines, the pistons are different but im sure they are no stronger..
I'm personally against the higher figures, as having experienced a mid boost clio anything north of 280 bhp is just horsepower lost in tire smoke, and im pretty sure my old 260 ph1 would keep with your m5 anyway :tongueout: