I get code P0301 Cylinder 1 misfire but no check engine light.

Yes it is actually misfiring. Can you advise? Thank you

Maybe, provided ALL the basics have been proven to be ok (?) .. Are you afraid of spiders? .. Google > 98 Yukon fuel spider for reference picture .. Good mechanic with a fuel pressure test kit should be able to diagnose... Hint: Look for 'telltale' sign > fuel pressure leaks down immediately after engine is switched off .. [Fuel injector failure will mimic ignition misfire] So will vacuum leak *at idle rpm* - as casey40510 stated.

Thank you but we already checked all that out including the scary "spiders" and all checked good. We have a vacuum leak which has proven to cause our misfire code and effect fuel trim. Thank s for your input.

We try! .. Thanks for replying...

Thank you. We thought it more than likely was a vacuum leak. We had checked everything else out including the distributor, 02 sensors, spark plugs etc. and all was good. We just finished replacing head gasket and checked the valves, push rods, hydraulic lifters, rocker arms, injectors-all was good. We greatly appreciate your help☺

No problem, just hearing we could help is thanks enough. let me know if you need anything else.