..I'm just not sure how much performance improvement was due to the TB cleaning/mod and how much to the spark plug replacement..

Yeah...and is it possible some of the improvement might be subjective too...but anyhow, I like that and since there is no harm doing it, and I already have the dremmel <img src="/forums/images/graemlins/pfft.gif" alt="" />, I promise I'll do it too on my next pass in that area... even if it turns out just for the elegance of the air flow, and take the "before" photo that is missing above.