technically correct, MCO wasn't released as part of the NFS series, though it was conceived and initially developed as an NFS game. Once EA got their clasw into it with that early 2000s MMO bug that was going around as the next big cash-cow, they butchered it and turned it into MCO.
That still sits as the best "car" game I've ever played.
SOOOO much customisation, so much room to mess about in, so much to expirement with and fine tune. It was a full-on hotrodding experience.. none of this shitty arcade "engine package 1", "suspension package 2" shit. They had a bajillion different everythings. Intake & Exhaust manifolds, heads, valve trains, camshafts, carburettors, turbos, blowers, exhausts, sway bars, springs, shocks, wheels, tyres, spoilers.... everything, all actual parts, officially licensed and accurate. The thing even had (proper, third party simulation) dyno software built into it that would take all the bits and pieces and throw it through a simulated dyno to give you torque and power curves for your car.
I hope this does that memory justice. I don't hold much hope for that, though. It's just too detailed for the way the NFS series is these days, with it's freakin neons and decals for all the ADD kiddies.