I fitted mine after stage 1, the ECU should adapt to the extra air intake. Tbh I can see it being 2 things, either it's not fitted correctly or you're expectations are too high. Where are you based mate, if you are local I would be happy to have a look at yours and give you a demo of mine?
I don't think the DV will be an issue as even when mine had a half inch split in it, the intake still made a noise. If you are thinking of swapping DV's don't pay out for the Forge, go for the Rev D OE type, less than 60 quid from TPS.
Not sure if this will help, its not the Evoms, but the sound is almost identical to mine, not sure about the engine noise though, sounds like a tractor.....