I can tell you from experience to get rid of the bosh platinum plugs and go with autolite or the champions. When I put the bosh platinum in my 99 it ran like crap at all speeds. It felt like the engine was going to explode. I immediately turned around and put my old plugs back in. returned them to the parts store for some cheep ole copper autolites and WOW! At 1.99 per plug I would try it. You can always return them if it doesn't help. However, I know the problem you are having and have seen it before.