split air pipe clogged.
 

While I was cleaning up my split air pipe I tested the check valve to see if it was still functioning. It checked out fine, then I tried blowing into the nipple that feeds backpressure to the 5th and 6th port actuators. Hardly anything made it through, I inserted a toothpick into the opening and it stopped well short of the depth to reach the back of the main line it comes out of! Something was obstructing it where it was welded. I thought maybe it was some carbon buildup but was not able to clean it out.

I then tried turning a 1/8" drill bit by hand but was unable to clear it out. So, out comes the cordless drill and I tried by running the bit backwards to no avail. I carefully drilled in the forward direction until it bit into the obstruction and stuck! It definitely was metal, probably from the weld. I was successful in drilling through it, without drilling out the back of the main tube! After a bit of carb cleaner flushing air moved through it just fine.

A small thing to overlook,
https://cimg6.ibsrv.net/gimg/www.rx7...67db1548fa.jpg
https://cimg8.ibsrv.net/gimg/www.rx7...d2e3e7d825.jpg
but it cost me hi-end power from the day I bought it off the show room floor!