I had the same problem...I took it off and put a second hand system on as the mongoose is such a bad fit.

I re fitted it as its new and fook me was it tight. Proper shit fit no matter what you done with it. You must use poly hangers to stand a chance.

I left the 3 nuts on the turbo loose and propped it up with trolley jack then twisted all of the system until it cleared everything the tightened up the clamps, and last of all the three nuts.

However, I e not put the bumper back on and garauntee it'll be a mile out

Blueflame fit like a glove and have proper flanges in but th entail pipe is slightly to long, that's where my money would have been if I'd of known at the time