I once had a rough runner on take off and was losing 500rpm a time. I just carried on a normal, did a climbing turn up to 800' to stay close to the airfield and gave a downwind call as usual; there was little else I could do..... I felt happier flying a normal circuit than trying to be clever and do a turn back or start finals early. Runway infront of you is always a good thing!
Didn't bother making a PAN call....