I recently upgraded the exhaust on my 533 to the Borla stainless exhaust. It was $200 cheaper than the B&B and has a million mile warranty. Below is my original post.

I received my new Borla stainless steel exhaust last week and got it installed over the weekend. I wanted to pass along my experience.

1. After I ordered it, I was informed that it would have to be built since they were out of stock. Not surprising since it's for my '84 533i (same model as the 633). I took delivery about 4 weeks after placing the order from a local sport shop for $510.
2. The new system was shipped in two parts, the muffler and the pipes (replacing the resonator) which bolt together with stainless clamps. It has the intercooled tips which are highly polished, although they stick quite a bit farther than my previous Bosal system. The new tips are just within the rear bumper. I looked through the muffler and was surprised to be looking all the way through the muffler. It has a straight pipe running through the muffler with perforations in the pipe within the muffler.
3. The installation was fairly straightforward, although not as smooth as I would have liked. Finish = A The weld and other manufacturing details were very good. I also like the fact that it's not mirror polished like some others. Fit = C I was a little concerned when I heard they were going to have to build my exhaust and who knows how old the jig is. The welded on plate that butts up to plate on the cat was welded slightly off requiring me to use several screwdrivers to twist it around slightly to get the bolts in. Also, once the entire exhaust was in place the two hangers (near the original resonator) were both pushed to the right side of the car. The pipes were not bent properly to make the exhaust run straight down the car. It's tolerable, and nothing rubs, so I'm living with it. The new hangers I used in my infinite wisdom were much more flexible and easily accommodated the new setup. You should also make sure you have new mounting hardware from the dealer prior to attempting installation (gasket - 18 30 1 723 881, gasket ring - 18 11 9 067 822, and new bolts. These were my part numbers, just for reference.) Sound = A- I never dreamed an E28 could sound like that! The only reason I give it an A- is that it might be a little too loud :-) Performance = ? The engine definitly breathes more freely and revs quicker now. I'm only quessing at some of these assumptions, but here they are. I feel like I have less torque now, based on how much the engine seems to pull under hard acceleration, but at the same time, where the engine used to "lug" (i.e. 4th gear at 2K rpm) it now runs and pulls effortlessly. This is further confused by the fact that I have a 535 engine with 533 electronics and exhaust, which is smaller than the 535 exhaust. I also notice that I "seem" to be at speed quicker than I used to be and I seem to be driving faster now.

Overall, I'm quite pleased and would recommend this exhaust. Currently they only make it for the 533 model in the E28 family. The 533 used 42mm pipes and the 535 bumped up to 45mm, cat back. Based on the age of the cars, I wouldn't expect that they would build one though :-(

Scott