hey, put a xforce twin stainless system on my BF XR8 and when i picked it up from the exhaust shop the mechanic said there was a big bush in the rear end that has s#$t it self and told me it is not a cheap job to fix. Does any one know what this bush could be? The car does make a clunk noise when driving slow.

Diff cradle bush, actually 3 bushes, 1 centre rear and 2 outer front. Do a search, very common! Getting mine done this week.

Thanks blueblood. that was the problem but least of my worries. Now i have a new problem. The motor has become slugish, struggles to move, makes a mad ticking noise (sounds like tappets) now and when it is dark outside, i lift the bonnet start the motor and i can see a spark going between the rocker cover and head. Would that be coil packs? The car is coming up to 115000 km, it must be true what they say, buy them new and get rid of them before 100000km. I don't know much about new cars, i'm use to driving old falcon/mustang V8's. Nothing like this thing.

Seeing spark definately sounds like a plug or coil packs, I'd be looking for the source of the spark. Is the ticking in time with the spark? Mine has 270k on the clock (but I've been in worse with 100k!) and one of the first things I did was coils and plugs which made a big difference! But doing that showed me I also need to do the rocker gasket and the o-rings between the rocker and the spark plug holes in the head. Oil got in around the plugs and coils and caused a misfire which stopped after I replaced the coils/plugs but is slowly returning. So this and a few other issues gives me a bigger to-do list than my 330k 1993 XR8
Im a little like you I've been in E-series V8s for the last ten years, (just put oil in one end and fuel in the other and drive!) so I'm learning alot too.