98xp

Hey I'm working on a mates 98 xp engine type 947 and just came across something I'm not to sure about. The oil light just came on but it the ski runs pre mix. He bought the ski off a guy that gave him no info about the ski. It still has the oil tank in the front with the sensor still...

I have recently purchased 97 and 98 XPs, and the 98 has issues with acceleration. From a dead stop it boggs bad when opened up. Even when it is plained out it won't rev above around 4500 rpm. The manual suggests flame arrestor cleaning. Has anyone experienced this, and may have some advice?