Welcome to the 135i club! Sounds like you picked up a nice low km car.
I agree that downpipes and FMIC are probably next on your list. If you're bumping up the power with MHD make sure the car is reliable first. New spark plugs and coil packs are highly recommended. Keep an eye on the stock injectors, water pump and high pressure fuel pump too. If well maintained these can be very fun and reliable cars!
