Motoring sound on accerelation

[306Puggy]

This is a hard to describe sound but low in the rev range there is a "motoring" sound sort of like a V8 sound mixed with gurgling. I don't know whether the manifold is blowing but it shouldn't be because I've got a new gasket on it. There also seems to be a pressure building up sound higher up in the rev range, I'm not sure whether they are linked or not.