Setting climb RPM and applying power, the engine started to miss and surge. Sort of drifting back toward KLUD, I played with the RPM and throttle setting. Anything over about 34 in MP and the engine stumbled and surged. With T/O RPM and full throttle, the engine simply died. Throttle back to below 34 in MP and it ran OK. While playing with the throttle, I was turning circles to the northwest of KLUD when the sun happens to shine on the fuel sight gage. There's crap in the fuel in the sight gage! You can see it when the fuel in the gage moves up and down with the slosh in the tank.