Well I probably should have done a pre-swap dyno, but oh well.
I ended up springing for the TMS headers. I put them on last weekend (Boy, what an experience). I still need to attach the midpipe, etc. to the headers, though. I figured I could use the existing studs/nuts, but the studs don’t hold onto anything and I can’t grip them with vicegrips well enough to get a good seal. I’d like to replace the studs with appropriate bolts. I’ll try to do that this week.