when i boot it in first second third or fourth around 4.5 - 5 k or so i sometimes get a pretty loud like croaking noise. sounds like its coimng from turbo/ uppipe kind of area, but again im driving quite fast so cant be sure.

and i just had a look before anyone suggest, and there arent any frogs under the bonnet, or hanging off the uppipe

recently fitted equal length tubular manifold, and lost one of the screws for the heatshield, so only got two of them fitted. could this be it