To clarify: You have a curvy (2002) SV650 and have widened the plastic entry hole in the centre of the air filter to make it more free flowing?
If this is the case, put the old one back in and see how you go. My suspicion is that the mixture may become leaner at high RPM as the carbs are not suited to the non-standard filter.
If the problem goes away with the old filter fitted you have your answer
Jambo