I haul logs with my 1998 ch 355/380 (last six 107636), and here about a month ago I was loaded in the mid afternoon and the temp was in the mid 90s. Out of nowhere I started to hear a popping and surge in RPMs (about 50 to 100). I've heard this noise before, it sounded like it was firing back out the intake. The water temp had been running warm around 200 the motor derated and struggled. I got to a small town and slowed down trying to find a place to pull over, got stopped looked and listened around got back in and it went away. Next day loaded midafternoon samething. This went on for two weeks so I put it in the shop. First checked the computer, replaced air intake temp sensor and both engine position sensors. Next ran the rack on it, some of the valves were a little tight. Mech. said your fixed and I left. So the next day same thing and still running a little hot, ran it for a while took it to a different shop. Ran the rack again checked the cam kept it for a week and said "I don't know". Ran it for another week and put it back in the shop. Two rebuilt heads, new thermostat, checked cam AGAIN a few other odds and ends and "your fixed". Guess what, it aint. I took it home and cleaned out the rad., intercooler and condensor. The next day it ran cooler, had more power, and did not make the noise again until I ran it hard and came into a mill and lugged it a little and POP. It had gotten where it did it all the time loaded rarely empty and once cool nothing. Now it does it after running down the Hwy. and going back through the gears with temp 180-+. Out 5k not including down time this sucks.