Here is a link to an entire thread on these.
http://www.m42club.com/forums/showthread.php?t=259I never personally installed it before I got rid of my e30 but here are some quotes from the thread I bought it from...
"91 octane. Raised rev limiter. Smoother idle, noticeable gains after 4k. Had on my car for about 3-4 months. Nothing wrong with it at all."
Like I said, never used it. Just don't have an e30 anymore.
If interested, send payment via PayPal to dmstrzelecki at gmail dot com and I will ship promptly with tracking.