I have an APR ECU upgrade, Forge DV, and Neuspeed P-Flo intake. When I added
the intake, I noticed that a) the engine got way louder, but b) during long
accelerations I often hear this strange sputter that sounds like air going
in the wrong direction(?).

Anyway by long acceleration I mean that I have the engine in a higher gear
(say, 4th gear while going 30mph) and hit the gas > 50% for about 4+
seconds. If I downshift the engine responds quickly with plenty of power,
and this only happens when I'm not trying to accelerate too quickly and get
lazy to downshift.

I'm currently using the softest spring in the DV and did try the next
stiffer spring with no difference.

Just for the record, the sound goes something like this...

jjjhhheeewwwwwwww-kchh-sput-sput-jjjjjjjjchew....
-----------------------^^^^^^^^^ - the sput sput is odd...

Any ideas?