Hello everyone - new to this forum, but have been a lurker for awhile, researching the issues on a 2006 Sportsman 800 Twin EFI and looking for some additional guidance as I am stuck....

Background: 800 twin has only 1200 miles, picked up used. Have two other sportsman 500's which we use daily on the ranch, one with 7K+ and the other w/10K miles. They get full fluids change out every winter and other scheduled maintenance (plugs, wires, brake/boot inspections etc.).

As I did not know the maintenance background on the 800 twin EFI, I changed all fluids per usual, but was still running "rough", rich on the fuel side (exhaust), poor to no idle, but when I gave it full throttle it has full power, no stuttering, surging etc.. Checked codes and 41/45 came up, Replaced the TBap sensor and wiring harness and cleared the codes. Ran better, but still not where should be.

Previous owner changed the spark plugs/fuel filter due to rough running. I removed the spark plugs, set proper gap (0.035) and installed new spark plug wires as they didn't ohm consistently nor snap in place properly and also cleaned the throttle body plate, checked the boots etc. (all fine).. Also ohm'd the coil which came in @ 636 Ohms, slightly above the 560 +/-10%, Idle has settled in @ 1080, no rich smell on exhaust BUT...still hesitating/surging when constant throttle applied (power, no power, power, no power)....HOWEVER...when I give it the nuts (full throttle), she goes no problem, no backing off, no loss of power, just constant climb on power. When back off to constant throttle position, back to surge, hesitate - may settle in @ 2900-3200 RPM, but then if back off or press slightly, back to same surge. I am running 91 octane w/a can of seafoam in there, but don't believe fuel/injector problem, spark problem.

My gut says TPS (throttle position sensor) which is a dealer deal. Thoughts on this or links to how others may have solved it (other threads)?

Any assistance would be appreciated.

Thank you - SDman