2003 Impala with 93,000 miles. For about the past 30,000 miles will not start on the first crank every once in a while. Starting to do it more frequenty. Now when it does it I have to hold the pedal to the floor to get it to start and I need to keep the RPM's over 1500 - if I lift off the pedal the RPM's will just slowly drop to zero. It has gotten bad lately and I need to do this 3-4 times. Then I have found that if I do a " brake torque" to keep the RPM's up and then start driving, it usually works (stalls once or twice still sometimes). Did the other day and has started OK since. Have heard fuel pump regulator. I do not detect a strong fuel odor at the vacuum line (as some have said) - hard to tell.
Related: Drove out to Colorado once around 75,000 mi. Noticed poor fuel economy. Got to the mountains and power was poor - backfired once. On the way back was really bad. Once back found that I blew a hole athrough the intake manifold opposite the EGR return. Dealer said had a clogged catalytic converter (but gave no other reason). I suppose it makes sence if excessive exhaust was forced through the EGR and literally torched a hole. Related?Incidentally, when the dealer replaced the intake, it had the starting problem when I went to go pick it up and I left it there. The next day had no problems when they checked it. I had the start problem before the intake manifold problem, but never that bad.