So i just got a 89 rx7 fc GTU 115k miles , and ive had to fix some things , and now its running like crap. I need your Help .

I got it in Feb .
My fuel pump went out , changed that . It Ran good but i was thinking tune up . So i just bought spark plugs , and a air filter, Changed them out . also bought a fuel filter but didnt put it on.
A week later . My check engine light came on . And when it would come on it would jerk then slow down and not pick up .
I got a jumper wire and checked the code . I got code 9 (water thermo sensor) , I changed that out and the thremostat too might as well .
Drove it slow around the block . Felt fine . n then when i took to the road n picked up speed the check engine light came back on . (still on )
I did the jumper wire again , and it didnt give me a Code ? ,,
it feels like crap guys .

Is there something i missed ? or some i should do .

 

wait until it spits a code.