2005 supercharged 3.8 grand Prix issues
I have 2005 grand Prix gtp with the SUPERCHARGED 3.8. With 88k miles I replace the
lower intake gasket & scharger gasket cuz of lack of power an codep0300 mult random
missfire . didn't help changer coils even swapped off a buddy's car still nothing. Changed
the cat for bout 2 weeks car ran quite nice went back to doing the same thing. Tue cat
was the mid grade version that Napa offered ran like 375$ I believe part only. What's
going on? Also now cuz of money issues had to continue driving the car I've got lifter
noise. How much difference will I see if I hollow the cat out or put straight pipe in? All
suggestions welcomed