agreed i should have read the whole thread but depending on the type dump it can still be usefull, if it is a straight through pipe then no it is a useless test, but if it is a chamber type with the usual 3 bolt flange (and 02 sensor bung placement) it will still show up any restriction, even with the exhaust dropped. We just used this to sort a restriction in a s15 that had a dodgy china split dump, then tested the tomei and CES (tomei was the pick).