You can clean the TB with brake cleaner. To clean the MAF use only MAF approved cleaner. I know its like $7 a can but it won't harm your $150 sensor. The backside (the side that you can't see) of the TB butterfly gets carboned up and can stick open a bit causing wierd stuff.
Good call on the coppers.
Does kinda sound like an exhaust leak. They usually seal up once everything gets hot. I've had one at the rear mani. on my 00 GT for a while now that I need to take care of.
Don't know about the timing chain tensioner. Haven't done that one yet. I do know that the chains themselves last quite a while though.
