Throttle adjustment on a 1998 3.8L Mustang

What's the proper throttle adjustment on a 98 Mustang? I had a friend tweak
the throttle a few months back when I had an 02 sensor issue. The sensor
has since been replaced (check engine light off) so I was thinking the
throttle adjustment could be out of sync. The pedal feels soft and the
engine occassionally "warms up" on extremely hot days. Idle speed is just
below 1000rpm. Also, the transmission seems to struggle at lower speeds
but on the highway it shifts just fine. Can an improper throttle
adjustment be the problem? It's been a couple of years since my last fuel
injection service but other than that, the tranny is good and the cooling
system was just recently replaced as well. Let me know what you think.

Thanks,