Cool..
The tool is a good addition for that chassis b/c that is the last of the owner accessable Flash Code retrieve... anything after that and you have to get an OBD2 scanner.[ or go to Autozone, etc]

... so , woth the $5 and a little soldering...

You will notice that these late Flash code ECU have quite a bit of storage/diagnostic capabilities , so may as well go in there and see what they have to tell you...

On the spark plug connectors , the common complaint is usually caused by the failure of the connectors under each coil as they are trapped with the engine heat and they rely on a friction/spring pressure connection [ I don't like the design] , whereas the other plugs have a snap connector [ much better]... anyway , b/c the coil fires 2 plugs in series [ waste spark system] , any poor connector in that 2 plug series circuit will cause a misfire , as the spark has to complete the circuit back to the coil instead of to ground like on a conventional system,
Remenber , those connectors are also the plug RESISTORS, so you can not tell a bad one by looking [ unless your x-ray vision is better than mine .. I never fully recovered from that blast of Kriptonite a while back ...]