02 R6 Surging and Low Idle after Rev

[ABSOLUTNATI]

After my bike is fully warmed up, it has issues surging, mainly in 1st and 2nd gear cruising around 4K-8K RPM (25% throttle). If I open it up above 50%, it accelerates fine, except for 1st gear. That usually stays surging above 8K. Low speeds are difficult, especially off the line. If I'm at a light and give it a good rev, the idle drops below 1K RPM for a couple of seconds, then goes back to normal. The idle always kind of moves up and down by about 100 RPM's. I installed new NGK CR10EK pre-gapped spark plugs, new Mobil1 4T Racing oil and STP oil filter, new OEM fuel filter, and 2 back to back 4oz. Seafoam treatments in the gas tank, so I doubt they are the problem. Should I bite the bullet for a carb cleaning and sync? Or is there something else I should try out or worry about? The bike did die out once while riding twisties one night in second gear around 8K RPM's. It started surging real bad, then finally quit during midturn. Kind of scary! The only mod done is a Yoshi TRS slip-on pipe.