Recently purchased this 2001 ZL600 EFI with 2300 miles on it. Rode it 3 times for a total of 400 miles, it ran ok but lacked top end. This is my first EFI / APV sled. Cleaned the exhaust valves (definitely carboned up) and adjusted the cables. Pulled out of the garage and now has great top end however once you back off the throttle to turn around it bogs to the point that it will stall. Will some times accelerate after allowed to idle for a few seconds but only if I feather / pump the throttle. Other times I must shut off and then restart and the cycle starts all over? My first thought was fuel problem and I checked the fuel pressure she holds steady 40psi even when it woun't accelerate. Disconnected TSS no change. Took it to the dealer and they checked it out and told me CPU checks out fine and they "think" it might be a TPS but cat only sells it complete with throttle body $1,200 - $1,300? I think I've found a used TPS but hate to throw good money after bad. Anyone out there have any ideas?