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I have two of these models (Hisun) and both have the same issue. It started out low power and then one got so bad it would not start. The local Cub dealer did not have a scan tool to check so after I exhausted all the possibilities I could think of I took it to a local small engine shop who worked on ATVs. After 2 months and $1600 later we got it back and it was running great. They pretty much replaced everything fuel related, fuel pump, spark plug, fuel injector, intake boots, throttle body, TPS and did an oil change. I ordered everything on the list for the other unit as all these things are pretty easy to replace. Before all those parts came in the first unit began to lose power little by little again. I went by the shop and asked the tech for more info on what they found and he said the fuel pressure was about 60psi and should be 40psi and that was causing and over fueling issue. When I told him about what had happened he thought it may be another fuel pump. I also asked if they had adjusted the valves and they had so I rechecked the valves and they are good. After searching the web I tried to relearn the TPS with instructions I found pertaining to a Massimo 500. Well it started to idle better and also seemed to not pop back through the intake like it was doing but only up to about 60% throttle. After that it bogs down and runs like crap. Tried the procedure on the other unit and now have the same result. What am I missing and/or doing wrong? Any help or ideas would be greatly appreciated.