94 celica st overheating issue, 1994 celica st 1.8L overheating issue. Options

[rapid36]

Hi i have a 94 celica ST with the 1.8L motor. I bought a used motor from online that had 132k miles on it. i dropped it in and i replaced the following on the car:
1. rear main seal
2. oil pan gasket
3. torque converter
4. radiator swapped out with 3 row performance radiator meant for gt4.
5. added a 15 row transmission cooler
6. new air filter
7. new spark plugs
8. new spark plug wires
9. new front o2 sensor
10. new fuel filter
11. straight pipe headers
12. high flow cat
13. aftermarket muffler
14. new belts all the way around

and so when at idle everything seems fine and when i drive around town everything is fine but only when i get on the highway going 65MPH it starts to overheat very quickly and then i pull over and let it idle and it seems to go back down then i drive again and then at this point going any speed is making it overheat. i have no check engine light. and i checked the thermostat and it works and i checked the water pump and it works. i just flushed my cooling system and no luck there. I dont get why its overheating on me. I checked the compression and all cyclinders show 150. no noises are being made and when it gets hot the car runs fine no missing or other issues just gets hot. Anyone have any ideas?

[Smaay]

im 95.87% sure its your head gasket. a compression test will confirm.