FST Pro's worked wonders for mine, I'd started to wonder if I'd left a spanner in or something
Good stuff. Also, if your fuelling's already a bit off- as it may well be with a slip-on fitted- then winter tends to accentuate that. Cold air is denser so if your bike is already on the lean side, that could make it leaner...
Try sticking the baffles in if you don't have them in usually, see if that makes any difference.