Just do a tune up, it's really easy on these 3.8's..
Plugs, wires, coil pack = less than 100$ bought all together..
Air filter, clean MAF, IAC, IAT, Etc.
Basically clean up everything and tune up things, even if the problem is solved, Its an old car with 100k+ Miles, tune up everything.
1998 Mustang V6
CAI, Exhaust, Weight Reduction
16.5 1/4 Mile