Sorry for the tardy reply, been swamped.
The flow tubes are the short sections of tube that connect the midpipe (X, H, catted, o/r, etc.) to the mufflers. The only things that are different between the Magnaflow
regular and Magnapack catback kits -other than the mufflers- are the flow tubes!
I cleaned up the old flow tubes and 'Packs, wrapped them up, and sold them as a complete kit.
Call MagnaFlow and ask them for the tubes and mufflers. The parts should be readily available.
I swapped out the 'Packs to tone things down a bit. I love 'Packs on Mustangs but my favorite passenger (Spouse) did not like them on my car. The regular Magnaflow mufflers are just right for everybody in my family now!