Motor is running good for 20-30 minutes then starts searching for rpm's. No change when I put on choke. Compression is 90psi in both cylinders (cold), bumps 3-5 psi with a squirt of oil in the cylinder. With this, I assumed it was electric since it didn't change with choke on and compression is well within range. Put 2 new coils and plugs, no change. Cleaned fins etc under shroud, no change. Beginning of the season I put on a new carb, maybe I should put the old one back on and see if it changes??? Any ideas as to what to check next?