My 89 GT has a thermo sensor at the bottom back of the radiator on the passenger side. (pointing towards the block) When one of the connectors broke off mine a couple years ago, NAPA had the part. I recall it being $15 or less. $55 is a price that earns the designation "Stealership."
1989 MX-6 GT. ORIGINAL OWNER!! 315K on the original clutch, K&N drop-in, Gillis boost valve, Tokico Blues, OEM RSTB, Energy Suspension poly sway bar bushings, end links, tie rod end boots, AWR poly motor mounts (only the rear one now, and that will be back to a stocker soon - I got tired of the vibration and noise), OEM rear lower tie bar, PGT rear sway bar. Techna-Fit stainless brake lines, AWR trailing links, new OEM lateral links.