The motor is a 80's targetmaster with a MV4 q-jet, delco distributor/plugs - rebuild with 4000km on it. I've been getting what I think is pretty bad detonation as when I put the motor in I had no light so timed it by ear. Now I go to time it properly, and with the idle speed adjusted, vacuum advance plugged, air cleaner on. I started out with about 20 deg of advance, and that's where its been for the last 3 weeks that I've had the motor. Seemed to run fine, just pinged under load. Now I go to adjust it back down to about 8 deg advanced and when it's set at 8 it idles way down and bogs out sorta. Any idea what my problem is??? As far as I know the guts of the motor are pretty stock, but would a different cam want more advance?? Idle mixture?? I'm lost, any help is much appreciated.