Alrighty, like 2-3 weeks ago my car was hesitating when it would warm up to like 210. So, I changed the plugs, wired, put in a 160 thermostat and did the TB bypass. It got rid of the problem and caused the car to stay at around 160-180.
Then yesterday it started idling funny. Like it'd stay at like 450-500 RPM, like normal then kind move up higher slower like I was hitting the throttle so I'd have to brake harder. This without me touching anything. Then it would hesitate again. It hadn't done the hesitating for like 3 weeks. All this of course happened when it heated up to 210 again.
Today I changed the fuel filter because it looked like it was old and it was digustingly dirty. There are no codes and I am pretty sure it's not an o2 sensor because I get phenomanol gas mileage for my car. I am just curious if anyone has any ideas as to the problem if this doesn't fix it.

 

Maybe your throttle body is not completly closed, or is coming open, also check the idle on the throttle and adjust it if needed. Just a suggestion.