I have always heard cleaning the MAF with throttle body cleaner is bad and you should use MAF cleaner.. Using both I can tell a difference in both on my hands.. LOL If that is the case, if I were you I'd buy a throttle body gasket and just pull the throttle body off AND remove the MAF from the throttle body and clean them separate. (my opinion, others can comment)
Spark plug difference, I ran both 104's and 606's in my GT and couldn't tell a difference either way in the way it drove, but I always change my plugs every third oil change (~10K miles) since they are cheap and I'm in there (usually while I'm waiting on oil to drain I'll change them).
