I picked up a cool gauge made by Aeroforce called the "Interceptor OBD2 Scan Gauge" from a fellow on Kijiji (God I love that site!). It sells for over 300 bucks new but I scored it from a GTP owner for $150. Here's a pic:



It plugs into your OBD2 port and a switched 12v feed. This puppy will read just about everything your PCM can spit out as well as read and clear codes, do data stream recordings and perform a CASE learn (required after replacing PCM).
It's a slick little gauge. I can now measure SC boost as well as knock retard. Judging by my knock retard readings on acceleration mid grade fuel isn't good enough. I saw up to 4 degrees of timing retard.  I guess it's Ultra 94 from now on. I also can read see my trans temp and with the Royal Purple, it's running at 159 degrees (which is about 40 degrees lower than with standard ATF). You can have it show two constant readings or you can set it to scan every reading and display them in the two windows for 2 seconds at a time.
Ain't technology great? This gauge is available for most cars that have OBDII. The gauge also has two analog inputs for oil pressure readings etc.

 Todd