rough idle and tac does not work
 

I have just done an engine swap on an 89 325i. the idle is rough. if you give the car some gas the engine smooths out. When it sits idling it will speed up to smooth out every so often then drop back down. The other thing is that the tac does not work. Any ideas??

OK here goes, Fixed the idle problem, I had a vacuum leak thing runs great now. I also fixed the Tac. Had to solder new batteries on the SI board. I am down to a couple of electrical problems, most I have found the problems, one I can not trace is the check light goes off and the brake light on the led panel flashes. This is not consistent, it does go off every time I start the car. I touch the brakes and it goes away. Any ideas.

I might be wrong but I think it is supposed to work something like you are discribing. The brake light on the panel on both of my e30's have always has come on until I touch the brake, the system can't check the light until it lights up. If one of the bulbs are bad it won't go out.
By the way I,m having a similar problem with my tach.
Check out my thread, maybe you can help.