OK so I have searched and searched the archives but can't find any help so here it goes I recently installed a Megan downpipe everything went fine about a day or so after installation I threw a p0420 (common I know) but also threw a misfire in cylinder 3 so I assumed I needed new plugs went out and got some E3 plugs (horrible) car started misfiring under acceleration with those so I said screw this and went back to AC delco iridium plugs ran fine for about a day so now the car still misfires under throttle and Idk wtf please help or point me in the right direction???
Car is 2009 TC stock except tune and downpipe w/ k&n drop-in filter thanks for the help and happy new years

 

are the plugs gapped right for the car? sometimes u have to gap them differently for a tuned car i think

 

And proper gapping would be???? Thanks joe

 

no prob bro, i got my reference off modernperformance, under there spark plugs section it says what the gap should be for certain boost levels, check there site bro

 

Proper gap is .035-.032. Since your in a high elevation gap to .030. Also the e3s have been known to cause detonation issues so hopefully nothing is tore up.

 

could you elaborate on "tore-up"Mon just in case lol and thanks for the numbers bro I'm check em when I'm off

 

Detonation meaning kr. Which can crack or break ringlands. Rings, and ect. Internal damage.

 

hope its good mike, keep me posted

 

E3s are known to fry coil packs too

 

Thanks guys appreciate the help ill cover the bases y'all have mentioned and update as needed once again thanx and Joe hurry up and get back her bro lol

 

Thanks all that gave advice I regapped my plugs to .32 and no more misfires for now lol thanks again