We never mind helping someone who asks. Heck these poor guys and ladies on MVS have had to put up with me for years! Glad you have found a good set of tires. Much nicer knowing you have a good set under you!

Neil.

I would love to claim the mods make the site great but the reality is a group of 30-35 core posters who are proudly lady and gentleman-like make this site the best auto forum on the web.

Replace the light assembly.

The seals for the light have failed and are letting water in (obviously). You might be able to get a new seal, or seal it up with some silicone. Or as rspi suggested, replace the light assembly. If you don't want to buy new, easy to grab from a junkyard or find on ebay.

I think I still have a tail light from my 99 parts car in Classifieds. I drive BOSTON to pHL weekly so can save shipping too.

120 bucks is a lot. 35 bucks from salvage. If using sealer hit the 4 corners hard and clean well, I expect it's the corners where the leak(s) are. Might get it done for a few bucks. Seal well around the bolt insert areas. Don't over tighten or you will crack the housing.

Could be lots of stuff. What's the current status of ignition components? Plugs, rotor, cap, wires? How old is the fuel pump relay? Original to the car? If so, I'd think about changing if for peace of mind even if it isn't producing the current problem. How are the electrical grounds in the engine b...

Disconnect Maf connector,start the car and test drive it.If problem disappears...Maf is bad.
Other than that...could be a HUGE vacuum leak or FPR failure.
But,let's go one step at a time...cheapest things first!

Pretty near all of these suggestions should throw codes.
I’d start with a “2nd opinion” from another OBDll reader.

Basic engine/emission related codes are generic.
For now, most auto parts stores will happily come
out and scan your vehicle right in their lot.