Deep breath.

You should consider yourself lucky with respect to your system being pressurized.

Many, including I, have completed HG jobs only to have the next weakest link in the cooling system be revealed once the HGs held pressure. Sometimes it's the reservoir cap. Sometimes it's the throttle body heater gasket. Sometimes (as in my case) the old-style bleeder fitting in the old style top hose blew out.

What is excess pressure? Yes, as the system cools the pressure should subside, but many of us would be thrilled to have a system so tight that any pressure was retained overnight! This ain't your problem!

Now, back to the misfires ...

 

1 month later and I'm still getting all the codes. I'd like to think the misfires are resulting from poor sensor issues, however the misfires are on bank 1 and the bad 02 sensor code is for bank 2. Now, could be my cat converters that are clogged up... which wouldn't be too bad ($600) but I won't jump to that yet.


Also, definitely an exhaust leak. Can hear the constant ticking as well as the muscle car chugging when stepping on the gas. Can that be the cause of allllll these codes though? I see it as unlikely, but I'll work on fixing the exhaust leak this weekend