I picked up an Actron scanner at AutoZone. You have to also then get the cartridge that applies to the vehicle.
I was able to get my scanner and cartridge for 84-95 G.M. (except cerntain models) for $150 or so out the door. They sold it to me on clearance.
Come to find out that it is not compatible with OBDII. So, Actron will sell the newest scanner to anybody that bought the old one with the OBDII software for about $200 with proof of purchase of the original.
As is, the current model I have works great for the 90 corvette. It has current, historical, code look up, clear codes, instant mode, record mode/play back. It is EASY to use and has a large screen to view many things at one time.
However, it won't work on the 2000 vette. So, I will have to break down and buy the other unit as described above. The new model they have out will do both the newest cars, and the older ones, so it is a better overall deal.
The really cool thing for me is I will end up with a scanner that will do my 90 and the 95 3500 truck, and then a seperate one that I can keep with the 2000 corvette for a total expendeture less than just buying the new Actron system.
In any event, it is well worth the money to REALLY see what is going on with the engine. You won't regret the purchase price after you have diagnosed a couple of problems and saved the $50-$200 diagnostic fee at the local dealer.
Plus, when you get ready to pump up the horsepower, the scanner will allow you to watch some critical functions while you adjust your timing and fuel pressure, idle settings, and running tempuratures.