dvogel

Hello!

My name is Dave and I'm a new owner of a 2000 Miata. It only has 48K miles, bone stock, no rust, sat in a garage. Seller claimed that cylinder #3 had low compression. Was barely running when I looked at it. I towed it home and did a compression check (all good). Changed the plugs and coil pack and it came back to life.

Drove it around and it boiled over on the highway. (I should have known better because the coolant looked like mud). Prior to that the engine seemed restricted/low power.
Threw a CEL code of P0421 (warm up catalyst efficiency). I'm thinking the cat might be clogged when driving with bad coil pack/missfires.
I plan to do a leak down test as the seller gave me a piece of paper that a tech gave him after what the seller claimed was a "Compression Test", but I'm thinking he did a leak down test as the numbers were in %...indicative of a leak down test.

Bought an OEM style radiator, but I'm thinking I'm gonna return it and get a 2 row aluminum as I plan on tracking it in the future...Good father/son project.
any recommendations for anything above?

My thought was to do the leak down test and if it reveals an issue, then I'll pull the head and have it reworked.

The car is otherwise mint. It has 5 Speed,A/C,Cruise,Power Mirrors, Leather....so is it safe to say that it has a limited slip differential? Hard for me to tell.

Thanks in advance!
Dave