Last night at the drags was less then successful.. on only my second run for the night, the car felt a bit harsher then normal pulling through the revs. On the return road, I could hear this god almight rattling from the engine bay (it's very noticable - people in the stands could here it too.) Parked the car up and having a look, it seems to be coming from the back of the motor. It's there from the moment the engine is turning over and doesn't seem to matter whether it's in gear or not. I did try revving it to 1500rpm or so and it does seem to alter the rattle - seems to be a bit better to be honest. At first I thought it was a broken turbo but the noise is from further back in the engine bay. The general consensus is that it could be either a rear flex plate or internal damage. I decided against driving it home and stuck it on a tow truck. The car in question is a 2003 XR6T auto with 70k's on the clock. Internally its got Typhoon valve springs but the rest and the bottom end are all standard. It's running 13psi of boost with an edit from xtreme and has fuel injectors and a bigger exhaust etc to cope with that. I was changing at 5700 - 5900rpm during the run, exactly like I usually would. So, does anyone have any input as to what the problem might be and what can be done about it? Still did a 12.5@115mph for what its worth