Is This A Misfire..(put noise from exhaust)..?

Hey guys, im got a 95 4.6l v8 tbird that has 133k miles.. Every so often while i'm going between 10-25mph..i'll get a PUT noise from my exhaust..? This only happens if i'm easy on the gas..if i floor it, no problem.

About 3 months ago i changed my plugs, the stock motorcraft where platinum and where normally worn (light brownish pink color) and i replaced them with autolite double platnum plugs, which i gapped to the stock setting which is .054-.056... I remember at that time when i started the engine, it sounded like a chevy big block, this was because of the throttle body cleaner entering the combustion chamber.....wearing off basically.. PS i removed the plugs and a couple of them in the passenger side where coated with alittle motor oil..... I went to autozone, got the same plugs....installed all 8 just to be safe....then removed them after 20 min's run time...to see if any oil was on them...nothing..everything fine.

Now, i'm thinking maybe my plugs have an oil coating on them..? Could that be..? Another thing, ever since i changed my plugs, i've been getting more exhaust smoke then usual... The 4.6 is infamous for worn valve seals...so that could be part of it.

PS, wire's are fine..

I have heard of people having trouble with the double platnum plugs. Go back to the motorcraft platnums.

Yeah i'm gonna yank them out soon....i just don't feel like getting under the hood..lol.