SI-2 is the same as SI-1 only in a one tank package for BMW.Interesting observation thanks for pointing that out,if Redline is good enough for BMW to give SI-1 its own BMW part# then that says a lot.I'm sure BMW did much more intensive testing on this than maybe even Terry did,but as GMorg said the product has changed so i guess its possible Terry didn't do any test with this version.
http://www.redlineoil.com.au/product-information.asp
http://www.redlineoil.com.au/product-information.asp#fueladditives
http://www.redlineoil.com.au/product-information.asp
http://www.redlineoil.com.au/product-information.asp#fueladditives