You know the start up and then loses power and may conk out? I have thought this but....after camshaft sensor, throttle body clean and replace, sensor to the TB etc....I had the sneaking suspision all along. I found this embedded thread deep down the dark google hole....boom! I had already ordered the new ACDelco thermostat and temp sending unit....if you start yours and are having crappy gas mileage and overall performance, here is the key....if your car warms up slow and is below the center mark on your gauge, just next to it warmed up....and your car should warm up pretty fast....then the therm is sticking tell the temp sender to go rich....too rich. Boom kaput. Do it yourself through the left front wheel well or take into your guys...easy. picked up yesterday warm up fast, engine smooth, put in drive w ac...mileage bam, he also reset everything....gauge back to original warm position....that was the key...and it's the fix....just had this intuitive vibe. Start with this first and work backwards you'll be glad you did....thank you hope this helps....oh by the way the thermos on these are est for up to 100k miles....they say 85 to 100k replace.