http://www.auto-rx.com/
After reading about numerous products, I selected this one as it is a slow solvent rather than a shock solvent which can cause chunks to dislodge and block stuff. I really liked the effect it had on our high milegage 90 525 in terms of performance. Didn't do a visual inspection so no idea what the before and after looked like. Wow How could you keep from hurling at the site of that mess? That is an amazing picture.
I am sure you are going to get a zillion posts about switching to synthetic oil too. Let me be the first to say do it.
Dinan chip, Bilstein sports w H&R, RD sways, RD strut brace, 750 bushings, Zimmermans/MetalMasters, O.E. M Pars, Eisenmann muffler