Check engine light on - now what?

[rockind308]

Need some help. I have a 2008 H3 3.7L H3 with 2K miles that I had a K&N air filter system and catback exhaust system installed. Now I have the check engine light on, the engine is sputtering and on star diagnostics says the engine is running too lean. Now what should I do? Are there other adjustments I need to have done. Don't want to burn up the engine. Thanks for any help.