Something is not triggering the coil properly, or whatever switches power to the coil. I don't know anything about those cars, but I can lend some generic help. There are 3 parts really, something that triggers the coil (ECU, etc), something to switch the big power across the coil, and the coil itself. The coil sounds fine, and I'm willing to bet it's whatever switches power across the coil every firing cycle. It's most likely a bigass mosfet or something along those lines, it's got an internal short most likely, and is shutting itself off after 2 minutes because it's getting too hot. When it cools down it will work properly again until it heats back up. So take a look at the rest of your ignition system. I really don't know what type of stock ignition system you have though, so this may not apply to you at all..