Surging need help !!


I got a 99 with pc3, full yosh rs3 and airbox mod. I did the airbox mod about 2 weeks ago and ran ok considering I need to retune the bike but now for the last few days its surging at a steady speed at any rpm, if you twist the gas and the bike pulls the surging goes away. I tested the tps sensor and with the bike at idle the - is centered on c00 so that's good. and all the vac lines are good. Is there any other sensors that could cause this issue or do I need to be looking at a fuel pump and regulator.. I need help... :please: