I had a similar and very frustrating problem on a 25D not long ago. Turned out the owner did the HG's and timing belt himself and didn't properly torque the intake cam pulley bolt. It had chewed up the front of the cam shaft and allowed the intake cam to advance the intake valve timing about 15 to 20 degree's. This caused the compression reading to go UP on that side of the engine (about 220 compared to 185 on the 2/4) and resulted in 1/3 misfire codes, etc - just as in your case.