[John Rogers]

Compression leaks can come from several places:
- Past the valves, squirting oil in will not help increase it.
- Past the rings, squirting oil in usually raises it.
- At the cylinder/head joint, if you squirt oil in it should leak out when warm and show up.
- Out a hole (casting defect) in the piston or cylinder casting and possibly into the crankcase. If you remove the oil filler cap you can hear the chug-chug-chug of blow-by.
- Past the injector seal-ring, if hard or cracked or the plastic tip has disappeared and the small seal-ring is blowing by and it will also suck air inside, possibly causing backfiring on deacceleration.

If it were me, I'd check the last one before you tear into things.... Good luck