[&o]It was time to change my sparkplugs (almost 90K).I decided to try bosch +4 plug's # R3 385 or part # 4458. After installing the new plugs the engine (454 vortec) the engine was running rough. I had no time to check the problem had to go on a plannedtrip of 600 miles total.The truck ran terrible, when I returned home I changed the plugs back to a new set of AC 41-932's. The engine ran like new. All of the Bosch plugs were dark and oily.I called Bosch andtold my story to a service agent (Mike) .He told me to stick to original plugs in that engine and to call a techie for a refund (lost receipt).I asked Joe to get back to me as to what the problem was . After sending plugs to him I recieved them back with a letter.

Dear Mr

The sparkplugs submitted for inspection have been evaluated All of the spark plugs are gasoline and oil fouled. The submitted spark plugs are the correct plug for the application. No defects were found.
This situation would not be considered a warrantable condition and therefore Bosch can not provide any compensation assistance in this matter.Tha spark plugs submitted for evanuation are being returned to you.
We apologize for any inconvenience this situation may have caused you.
Joe Atteo
Customer relations
Automotive and Diesel Products

So does anyone have an idea why the old AC plugs ran fine, the Bosch plugs ran bad and the new AC plugs ran fine ?
This is not the answer I wanted from them mainly because I had such high hopes for these +4 plugs. I want to know why there plugs did not work. I know the Bosch plugs were fouled, but why.I know they didn't have many miles on them and they made the truck run rough at an idle, gave me poor gas milage, and less power. They ran bad, right from the start.

Rich C
Picture is of AC plugs with 90K and Bosch plugs with Appx 600 miles
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