Ted - appreciate the dyno visit support - really made the engine come alive!
Got some time in the garage...15 mins to drop the exhaust...a bit challenging solo...far easier than reinstallation, certainly.
And the culprit...appears I found the limit for self porting the tubes...little too much dremel power!:
Quite the massive leak...will see if I can have it welded closed.
Other comments...the X-ported blower may have picked up 1 psi compared to the 'Stage 1' previously. This is a bit lower than expected. The hotter dyno cell temps were significant even with the correction factor. +40 degrees F made the blower too hot to touch...