Welcome to the family of '99 V92C owners... You will end up learning more than you ever thought you'd need to know about your bike before long...
As to the immediate issue... Old gas can clog injectors; also, it the bike was sitting long enough for the gas to go bad, there may be sludge or other debris clogging the fuel filters &/or injectors - in which case, a through cleanout of the injectors and filters may be required. If it's not too bad, you may be able to get by with draining the existing gas, adding fresh gas & some Seafoam or other reputable injector cleaner, and running it to (hopefully) clean things out.
If you do end up pulling the injectors to clean or replace, clean out the throttle bodies while you've got it apart; some clean rags, some carb cleaner, and maybe some Q-tips to get to the difficult spots. (DON'T drop a Q-tip or bit of rag down the intake passages!!!)
Another possibility is voltage-related; if the alternator hasn't been upgraded and is getting weak +/or you have a weak battery, the EFI computer gets confused and goes into a "run like crap" mode. Check your system voltage at idle; if you have an upgraded charging system & good battery, it should read around 14 volts at idle; original charging system will only show 12 volts or so, and doesn't really start charging until above about 2000 rpm.
Finally, check the Throttle Position Sensor - if it's going out, it gives incorrect voltage to the EFI. This usually starts out as a miss or engine cut-out at highway speeds, and gets worse as it continues to degrade.
Do some searches here; lots of detail and experience on these (and other) issues.
'99 V92C with K&N, PMRT chip, Vic stage 1 slipons, and engine by Rylan Vos!