Revo Remaps cost around £500, and the SPS switch is around £150. The SPS really is a must, as disconnecting the cars battery will lose the Revo settings . The SPS is the only way to restore the settings (without a trip to your Revo dealer).
Revo will have written their maps using one of the mainstream suppliers (Milltek for exhausts for sure, couldn't guess which for intake. .), although will work fine with all other mods, it woulds best with the mods the map was written to.
I don't see how Revo would necessarily be better for a un-modified car? Revo wrote their maps when the GTI was new when all engines and components where clean and working correctly. As these cars are getting older and components are wearing or getting covered with Carbon, a generic map is treating it like new (ie asking for the full fuel pressure, where a sighting tired pump will struggle).
A tuner tweaking a map for your exact car will pick up on things like tired fuel pumps, MAF sensors not reading right, lambda sensors giving odd readings etc. . .
Tuning has moved on recently, where R-Tech have identified extra features to improve power delivery and figures (TIV mapping is an example of this). I'm not sure if other tuners are constantly developing their maps? With the fact that the mainstream tuners seem to be focussing on the latest models (mk7 GTI & R for example), I doubt they are too bothered about further improving the maps for the older models like the mk5. . .
Which ever way you go, either Revo or R-Tech remap will put a grin on your face
