Once your fuel filters are taken care of, follow the boost sensing line (white/translucent 1/4") from the ALDA on top of the injection pump to the overboost protection switch on the fire wall and to the banjo fiting on the back of the intake manifold. Remove the hollow bolt from the intake manifold and make sure it is not obstucted with carbon and gunk (mind the two copper washers)you can use cab cleaner and a small screwdriver to clean in out. If you remove the end at the injection pump you should be abe to blow through the line back to the intake with no leaks or obstuction. This will make a huge difference in how your car runs.

If it starts well in cold weather don't waste money on a compression check.