I ran G56 filter and stage 1 pipes for a year with no problems.
Have now had a remap at MMC they did it whilst fitting the cooling fan as the ECU needed flashing anyway and said it would effect the fuel consumption but I haven't noticed any detriment, it has a little bit more oomph at the top end now compared to the stock map.
In fact I averaged 39mpg overall on this years Swiss run to Grindelwald over 1500 miles in total.
