My Elantra 97 stalls on stopping, mostly at bottom of hills, hard to restart.

Seems like the Idle Air Control (IAC) valve is not doing anything. Try new (IAC)

i agree but scan codes 1st to see if it leads you that way

Re-check TPS adjustment.and throttle plate setting.Clean throttle plate if sludged , that will affect TPS reading .As for missfire, as globalhelper stated have it scanned (I recommend somewhere they can drive it and record a snapshot of when it's acting up most and analyze the data to see what area needs addressed.