Mavigogun,  You said you changed jets in the carb ,but you didn't say anything about doing the spacer mod, and we have no idea of your elevation above sea level. You say you can live with the bike doing 82mph, but the real question is can your bike live with it?  The fact that your speed fades and you must slow down is a sure sign that it's overheating from being jetted to lean, this can do some real damage. If your riding the bike at speeds high enough that your oil level is dropping (which is normal for this bike) , you could running lean , burn /drop a valve, or be blasting metal off the piston dome. I wouldn't keep running it that way.

Progressive Texas : latitude 31.4 degrees
                            longitude  -99.3degrees
                   
                            elevation 455meters/1495 ft
  your a long way from sea level.