Sportrak Engine light above 65mph


Hi all. I am new to Sportrak ownership and so far not having a huge amount of luck. So far I've had new clutch, new engine and new timing belt all in the first month of ownership.. I took it on its first run yesterday and when I hit around 65mph or 3750rpm the engine light would intermitantly come on and off cutting power. I noticed that if i drive in 2nd gear upto the same revs it happens but only when in 2nd or at motorway speeds.

Please tell me this is a simple fix thanks