I have a 4.2l 05 trailblazer. Got a P0304 error while driving the other day. Truck ran rough while pulling out but not to bad on highway home. The CEL alternated between off, on and flashing I figured since the highway was clear and no traffic and the truck was running better on the highway, I drive the 40 miles home Once home, I disconnected the battery after confirming the code with a scanner Changed the coil pack and now I get a P0300. Truck still runs rough but a bit smoother. Did some searching and read it should be a vacumm leak. I ma pretty sure i did not undo any vacuum lines but wanted to be sure. Are they any going to the air box i may have missed.