I know a cracked boot will lean out that cylinder and potentially burn it down. If you have one, and it sounds like you do, replace it. I would go ahead and replace them both.
A quick fix you could try and see if it helps your top end would be to wrap duct tape around the cracked boot. Go around the boot a couple times or so.
'05 Yamaha RX1 ER 1000
'93 Yamaha Phazer II LE 485
'96 Polaris Ultra SP 700 - SOLD!!
2012/2013 miles: 484 WooHoo!!
2011/2012 miles: 737
The sled is fixed...
Now my wallet is broke..