1993 Chevy Van Do I have leaky valves?

OK, so here's the story. My van was running fine but was long overdue for an oil change. Took it to jiffy lube cause I didnt feel like laying in the snow to do it myself. They changed the oil and flushed the tranny and replaced the tranny fluid. When I got it back, I decided to do a basic tuneup on it. Spark plugs, wires, distributer cap, roter button, oxygen sensor, air filter, fuel filter, fuel injectors, fuel pressure regulator, thermostat. Also I was having a problem with the heat so I changed the heater core. The van started running rough and I thought that it was a vacume leak. I checked all the vacume hoses and they were ok. Replaced the throttle body gasket and the map sensor. Still runing rough at idle. Problem has gotten worse and now the van wont start at all. I took the plugs out one by one and double checked the gap on them. Gap was fine but in less than 100 miles the plugs have a lot more carbon on them than I would have expected and came out wet with gas. Oil smells like gas too off of the stick and it is pretty black already. I have not done a compression test because I dont have the equipment to do so yet. Any ideas?