MK1 poor throttle response(low RPM)

[86black2]

I have an 86 mr2 and when i got it the idle air screw was rusted in place so i switched the throttle body out for one from an 88 mr2. the 86 is stick and the 88 auto when i switched i had to change T.P.S sensor because plug was different so was the I.A.C valve but i did'nt change that now when i slightly press on the gas at idle it starts to lope and is hard to keep within a specific RPM range (below 3k) is it the I.A.C? Would it be different for an automatic? Could I have hooked something up wrong? OR is it something else? P.S. When cold the car idles around 2k and drops to like 8-900 after it warms up. The car also threw an o2 sensor code on C.E.L could this be it? THANKS