[john]

You could do a leakdown test to see if the HG is leaking. I would guess that you have some boost leaks or are running a bit lean. As Jet said, a hacked Mas could contribute to it a bit also. I would do a boost leak test first as you should do one anyhow. Then if the car runs fine without an ass load of knock, leave it. I have pulled white plugs out of my car several times and not thought twice about them as the car was running fine. The car is probly just out of tune.