Service engine soon light flashed (01 S10 4.3 V6)

I've done quite a bit of repair on my S10. But most
recent problem has been in extreme rattle from the
exhaust. The rattle was coming from the Cad. But
while we were crawling around my sister spotted a
pin sized hole right after the header Right before
the Cad.
After patch in the hole and letting it dry overnight
the next day on my way to work I stepped into it,
and the RPMs raised which were followed by a
Extremely Loud pop and my service engine soon
light began too flash. The exhaust rattle is
completely gone.
Now I have a service engine soon light and a check
engine light I know it wasn't a misfire. I use my
Advanced code reader the engine did not throw
any codes all the calibration files are correct and
now my engine runs great so I don't know what has
happened.

I'm sorry for the share length of this. But I wanted
to make sure that you got the full picture.