my fuel economy has taken a hit but thats down to my driving, on a fuel economy motorway run at cruise controlld 80mph i get 36mpg, but that drops drastically when you press the loud pedal.
blueflame, piper, pipewerx, miltek all do down pipes for the mk5 platform. the piper and pipewerx are 3" i think the others are 2.75". might be quieter as well. ppipewerx were cheap as well have a look on ebay. they have a online shop, make sure you offer less than the stated price, i hear they are open to bartering.
I have manual, i love it now i have the short shifter. feels way better than std.
Revo has more adjustability than suerchips, you can change boost, timing, and fuel. provided you purchase SPS swich on top of the remap its also more aggressive torque wise.
bluefin can be installed by yourself from home though as can stage 2 and stage 2+, whereas revo you have to go to a specialist which means travel costs on top