I went in to buy a Stihl KM 90 powerhead today and they were sold-out -- so my dealer offered to give me the KM 110 for the price of the KM 90. In looking at the specs, may not have really gained much in power or whatever with the 110 over the 90. Bit the bullet and go the 110 anyway. I think I'm going to run the synthetic oil. I'm new to these 4-mxes and I'm still not too sure about them. When running the Stihl synthetic oil and high octane gas, do any of you guys still need to de-carb the exhaust port after alot of hours?