I doubt the tps is your issue. Likely the iac is needing cleaned or the vss is bad.
You have an 89 and it should be a maf car. So the pcm uses the signal from the vehical speed sensor (vss) to keep the idle up when you come to a stop and inbetween shifts.
you could also try cleaning the maf and throttle body .
Also the baffle inside the fuel tanks have been known to come loose , its there to prevent the fuel from sloshing away from the pickup while turning sharply or stopping.