Hello Paulie and welcome to the forum! Even without the CEL on, you can check historical and current codes without a computer (procedure in the manual), but i'm not sure it will tell you much.
You can also order a Bluetooth module (I like the one I got from Rev-Mo) that works with the program ECMDroid (free from Google Play) that will help considerably with diagnosis. This advise comes with the STRONG advise to NOT change or replace the tune. It isn't bad.
For now, how about the basics... Are the plugs clean? If it had sat for awhile, it is more than likely that repeated start attempts or a weak battery have fouled the plugs. They will act exactly like that in a semi-fouled state and it doesn't take much on a Buell. Iridium plugs work very well.
