Additional Checks

WARNING: This page is about a different car, the 2003 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.

Check the vacuum hoses for splits, kinks, proper routing and connections, and/or damage. See Vehicle Emission Control Information (VECI) label.
Check the exhaust system for possible restrictions. See RESTRICTED EXHAUST .
An engine miss condition can be caused by Electromagnetic Interference (EMI). EMI can usually be detected by monitoring the engine RPM with a scan tool. A sudden increase in RPM with little change in the actual engine RPM, indicates EMI is present.