As Brad said boostroller will make naff all difference to fuel consumption and certainly won't make it better. Your right foot is the best controller for petrol consumption
If you are considering a Dawes 'type' device. Then my only recommendation is get yourself a boost gauge fitted at the same time if you don't already have one to make sure your not over boosting or spiking boost badly.
They are crude but cheap and affective bits of kit, but they come with great responsibility IMO.
They can cause fuel cut, detonation, premature turbo/engine failure. etc. So should only be used if your a little mechanically sympathetic and savy, and accept the possible dangers.
You should be fine, but you Just need to keep an ear out for detonation and ideally borrow some det cans if you can.
I'm currently running one on my UK classic, along with turbo, intercooler and exhaust mods on what I think is still a stock ECU/map. Pulls like a train and no det.!