First of all, nice car, looks like you have done well.
WHAT!
Sorry for the interuption, but I think someone is getting mislead a bit.
I paid less then $3500 for a M600 with Loom, Datalogging, map sensor, water temp sensor and air temp sensor.
If your getting quoted another $3500 for installation, then I think you should give it a go yourself.
Computers are not hard to install at all, mine only has the three sensors, two distributor signals, 6 coils and 6 injectors to wire up. Not that hard and well worth saving $3500 for.