First thing I would be doing is replacing the CTS, this sensor is at the back left hand side of the head, it's a bit tight to get to, this is likely to be a cause of the problem, and if not it's worth replacing it anyway.

This, essentially, is a thermistor and tells the ECU the temperature of the coolant, this is an input which will determine the base level of fuel injected from freezing to boiling.

Over time though, being a resistor the output on these can go out of range, hence telling the ECU duff info, leading to your overfuelling.

Personally, if it were me I woulden't use a Krypton tune, I would use a specialist for a 'setup'.

Martin