[Steve Tinker]

Thanks Chris and jacabean for your observations, you made me feel a little easier.
Changing out inner driveshaft boots @ 5 x the cost of the delete pipe doesn't add up to me, so caution was the best option...
I'm still not convinced that the larger bore of the pipes have given me any added performance - in fact they seem to have have robbed a little of the mid range torque. I may bite the bullet and re-fit the originals back on (ugh - my old bones will resist again) just to confirm my butt dyno....
Perhaps I should have bought Che's 2.5 engine delete pipes - I seem to remember they are the same diameter as the Porsche pipes.