Distracted by an apparent cool running cylinder; the pilot of an SR20 canceled his practice RNAV approach and was cleared for a visual approach to the airport. Inadvertently; he set up to land at a closer airport with a runway with a similar heading. ATC advised of the error and the pilot chose to make a precautionary landing at the second airport.

Narrative

Conditions were VFR; with light haze. I was doing a practice approach (no hood) on the RNAV/GPS approach for Runway XX at ZZZ. I noticed that the EGT in cylinder #6 was under 1000 degrees; which was about 350 degrees below the other cylinders. I advised Approach that I had a 'minor' mechanical problem; and that I wanted to cancel the approach and go direct; and that I had the airport in sight. They approved my request; and turned me over to the Tower. When I was about 2-3 miles from what I initially thought was Runway XX; I realized that I was approaching ZZZ1 Runway XY. Just as I discovered this; Tower advised me that I was on approach to ZZZ1. I told them I would land there; and they approved. I landed routinely; and called the FSS to advise that I was on the ground safely. I was distracted by my concern about the low EGT on cylinder #6; and didn't go through the normal routine of re-programming my GPS to go directly to ZZZ. Given that it was directing me to the approach fix; it wasn't useful in directing me to the airport. I believed I had ZZZ in sight; and wanted to focus on flying the plane; and the distraction caused me to make an error. Also; I had the multi-function display on the engine monitor page rather than the NAV page; which was another contributor.