All my cars have Rare Earth, custom antennas, new gears, new motors. Nothing crazy like 4.2, just 2.6, 3.8, etc. I used to have custom exhaust, but they kept breaking off. Maybe I play too rough.
I'm about to do the layman's tricell to to of my cars, I just need to hit RadioShack this weekend.
I still love my Microsizer, but it gets blown away by my MicroSpeed cars. Ideally I'll get an Auto Modellista set and use the extra three bodies for my clones. That would be the best of both worlds.