Just thought I would throw my $0.02 in. When I was running the Link I started to have some "hesitation" issues. Since the Link gives NO CEL's whatsoever I had to figure this out without any aid. SO I pulled the plugs. They were brownish/red instead of black and suity so I cleaned them up with a dremel and everything is fine again.
BTW these plugs were one stage colder double platinum NGK's with only about 10,000 miles on them. I have another set just in case things start acting up again. But I was experiencing my problems during hard acceleration runs AND between shifts (bog badly).
Just a thought. It wouldn't hurt to pull one easily accessable plug to check and see what it looks like?