Two tabs open at 1 a.m. Left one: an 85k-mile E90 335i, six-speed, clean CarFax, $14k and the seller keeps calling it "basically an M3 for half." Right one: a 130k-mile E46 M3, Steel Grey, $28k, and every comment under the listing is somebody warning about rod bearings. The 335i math is genuinely seductive. N54, 300hp and 300 lb-ft from the factory, and a JB4 turns it into 400 with a tune and a lunch break. Nobody's lying to you about that. What nobody puts in the ad is the HPFP, the injectors that go out in sets of six, the wastegate rattle, the oil filter housing gasket weeping onto the belt, and the plastic charge pipe that lets go the first time you actually use the car. That $14k car has $6k of maintenance queued up whether you budget for it or not. It's not a bad car. It's a car that bills you in installments. Meanwhile the S54 is the entire argument. 3.2 liters, individual throttle bodies, 333hp at 7,900 and a redline at 8,000 that sounds like nothing BMW has built since. No t...