I will gladly second any recommedation to talk to Will Zaraska. I've done the research, weighed the options, and talked to a lot of folks: only Will seems to have the straight answers and formula for success you need to federalize a Euro spec E34 M5. This car (especially the 3.8 variant) requires some very specific handling to get through the EPA cold start test, and Will is the only one I know of that has a track record of getting them through. Frankly, at this point, I wouldn't trust anyone else.