My SES light came on and I pulled the code. It came back saying it is running lean. Where should I start to diagnose the problem? My spark plugs and wires were changed about 20k miles ago and the cap and rotor more recent FYI. Could a clogged cat be the problem? It smells pretty bad when the RPM's get up there.

Any help/suggestions/comments would be greatly appreciated.
Thanks

Check the voltage at the TPS. If it's low you are going to run lean. It should be between .45 and .55.