If it was factory equipped with a getrag 5-speed, it would have to be a '93 or older. They took that option away from the w-bodies with the interior redesigns in '94.
As idrivejunk said, a miss under any kind of load is usually either a vacuum leak, or ignition issue. I don't think routing is a factor so long as the right wires/plugs are connected to the right coil pack terminals. If they haven't been done in a while, I'd change out the plugs and wires regardless. If it persists, I know they're a pain in the ass to get to, but I'd pull out the coils and look at them. When I first got my 2-door TGP, it would miss BAD and had 0 power if I went more than 1/4 throttle on it. Drove it like that for a while, and then during one of the local w-body meets, one of the members just happened to look at and noticed that all 3 coil cases were split open like nothing I'd ever seen before. Switched those and the ICM out with new GM take-offs I had picked up on eBay for pretty cheap, and no more problems.
