Long of the short, dealer says shudder is caused by misfire and recommends plugs to be replaced. Figure I'll DIY once the weather warms a little. I hear a lot of talk about using the OE Motorcraft units, but Autolite does have a $2.50/ea rebate on their Iridium XP plugs, which would be a nice deal. Has anybody had good results with the Autolite plugs?

 

I would stick to motor craft plugs. Every truck that I have owned ran like poo with out stock plugs. If you do decide to not go with motor craft plugs the get a better brand than auto lite. Maybe go with NGK or or Bosch plugs but then again I recommend motor craft. This is just my opinion though.