I posted a few weeks ago asking about pistons for my 580 EFI. Someone said stick with Suzuki parts and thats what I did. Anyways my sled is still doing the same thing it did before I burned a hole through the top of the piston. I'm sure its just a matter of time before I hole another piston. The sled leans out the PTO side cylinder under prolonged full throttle. Years ago when I was shopping for a 580 EFI I had a guy tell me that his sled was doing this. After spending a small fortune at the cat dealer rebuilding and resealing the entire motor, they finally replaced the ECU and the problem went away. I really don't think the sled is sucking air as it starts, runs, idles perfectly. From what I have seen engines that are sucking air have erratic idle. There is a lot of oil residue on the front of the motor below the exhaust manifold. I'm assuming this is leaking past the exhaust manifold gaskets? I see used ECU units on ebay for $100-$300 - they are $1700 cdn from the cat dealer. A person can also replace just the EPROM chip. Not sure if this will fix my problem though.