Help ZXR250C - Rebuild V2

hey all, question...

So since she's back on the road, she feels, shall we say, 'sluggish'.
Rev's up to the full range, and I can't 'hear' any clutch slip, but yeah just doesn't feel as pokey as she did (I have dropped weight too lol).

Couple things to note:
- I noticed a bulge in one of my spark plug caps, possibly the cap is cooked and I'm just getting an occasional misfire?
- Clutch would have been sitting there dry for a fair while, maybe I am getting some slippage but not enough to notice by sound?
- I could check the carbs are still balanced but I would think if they weren't then my idle would suck and I would struggle to get the revs up?

While she's been out of action, I rode a friends DRZ-450 in the UK for a day, and then another mates MT07 for an hour or so.
Maybe she's not actually anymore sluggish than she used to be, bit just feels slow after riding torquey bikes?

Cheers
Dano