aLL FUSES GOOD.
all cold engines race high ,engine cold and the more cold the more high RPM.
1500 is PAR for RPM cold, is yours higher?
black SOOT is a huge bad RICH sign. of greatly needed engine service.
no code told P03xx what is XX.? (sad face)
we can';t guess codes we need to see them. sorry and all off them.
I thank also your scan tool is not certified for GM OEM scan codes.
P1xx up.p2XX ?
or is super old scanner useless
or just cheap $17 code reader ? also useless in the real world.
also did you know
P0300 to P0306 means misfire. (weak combustion) lots of clauses.
ever do full tune up, in 20 years, spark plugs , spark wires
distrib. cap and rotor? ICM bad,?
?????
Map sensor clogged
IAC valve stuck open , RPM not regulated.
Fuel pressure was low, how low?, not told PSI
low does not cause rich burn but sure lean burn and misfire sure.
spec is.fuel real PSI test is 60-66?psi. RUNNING engine.
if not pump or FPR are bad. yes pumps can fail weak easy.
the test is called the Injector fuel pressure balance test in the SM, service manual.
the rules are.(gas)_
1: good engine, (compression at spec) EGR not stuck open and CATS not melted closed.
2: spark good, we can not burn fuel with dead or weak spark.
we call this a tune up,. (or doing the service points (today)
3: bad fueling, last fuel is last. in the due to Physics.
bad fueling can be caused by (short list)
bad MAF , or MAP, FPR, PUMP, or injectors leaking or clogged.
IAC stuck makes idle controls dead.
to find it take real tools , and gauges, a real scan tool , 2008 or newer OBD2 scan tool is best, for sure GM rated
GM has its own OEM factory codes. (vast)
or get the car serviced in a shop.,,, Bingo they have the tools!
here is your spark schematic
all these can produce P03xx codes too, but was never told.
https://imgur.com/a/gw0cHYR