That is rediculously lean between 3000 and 4500rpm!
You'll need to either go back to stock for now (which is still rather lean in that area), or get a Kev mod/O2 controller sharpish. You really don't need to spend big bucks on a PC to sort this out; the only significant benefit of a PC is you can "fine tune" everything in small increments with a custom map. The PC is the perfect solution, but you'll have to ask yourself is it �400-500 better?

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