Got mine installed by BTM. The hoses promptly slipped/blew off and first had lagging performance, then CEL, then limp mode.
Took it back to BTM, consulted with Wagner (who had no problems with theirs).
Conclusion: BTM cut notches to match the stock IC so the snap rings would seat properly.
Reinstalled, everything is great. Should have experimented, but I would guess 1mpg better in my 75 mile commute. Instant fuel guage seems to read the same at 80mph as it did with the stock IC at 75mph. Scientific? No. Glad I did it? Of course!