Both UK and US e39 M5 Tubi exhausts are identical, and the weight difference is a misprint. 28KG is 61.6 pounds which is the correct weight for the entire Cat-Back system.
Manufacturers print "For Racing Use Only" to protect themselves from litigation. If the statement were true, then no aftermarket exhaust would ever be sold. The Dinan CARB certification is nice, but is really just marketing. My experience has shown that SMOG certification in California is never really a problem in 99% of the locations. If there is ever a problem or even more than a 10 minute delay, just put the beast in reverse, and drive down the street to one of the other 100,000 California SMOG stations.
For example, Dinan states that their headers are not legal in California. That is very interesting, since my beast was approved in California and passed SMOG the first time with their headers and plenty of other engine modifications. Here is the text from Dinan's website (www.dinanbmw.com
" The system is currently 49 state emissions legal*.
* This product is in compliance with U.S. EPA Memorandum 1A, or this product has not been found, nor is believed to be, unlawful for use under the provisions of the Clean Air Act. Currently: This product is legal in California only for racing vehicles which may never be used upon a highway."
To which I say: Yeah right!