If its DIY, its actually not as expensive as you think. The N54/N55 engines are also pretty damn reliable. The biggest problem i've ever had on mine was the electronic water pump going bad. Turbos, tranny, etc ran strong slight over 100k miles, car running mid 12s with simple mods and was a DD. Also gave me close to 30 MPG going to Las Vegas from LA.I would say HELL no on a BMW. To expensive when it comes to maintenance and repairs.
In Cali with all the stop and go traffic, that would be amazing gas mileage hahaGreat on gas?
22 city and 28-29 hwy with 25 on my commute isnt exactly great.
I had one for a quite a while.
4 seats is more realistic as the middle is useless.