One more bit of info to aid in the diagnosis. I just replaced the plugs with Bosch Platinums (WR7DP). I don't think the problem ever occured before the swap. I know this is a higher heat range but the plugs that came out were WR7DC's. I remember seeing a note or two about platinums for turbos. Did I do a bad thing? Thanks. Andrew Finney 1983 UrQ.