I have a 95WRX with a Uni-chip. When driving slowly around the town with very little pressure on the accelerator, at low revs (say between 1200 and 1800) I sometimes get a pinking type sound. The question is, is this Det?? I only sometimes get it. Or is this just a vibration coming from the engine, something like the mongoose down pipe opr likewise.

I know this subject is frequently getting raised and I am sorry for doing so again but I am rather worried!

Thanks for the help.
Mark