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when i first start my truck when its cold it runs great but after a while it just gets worse there is definitely a notable difference what could be causing that? just general wear and tear?
Wear and Tear will not only effect a motor when it's warm.
It's very likely that DD is correct and you need a new pre-cat O2.
You can try unplugging it and driving around, this WILL trigger your CEL, but you can tell if that's the root cause. (when you do this, do NOT drive it hard)