Very basic description would be that :
Stage 1 needs no mods just the remap
Stage 2 is just needs the addition downpipe and remap
Stage 2+ is just the addition of a HPFP
At any time you can add an intercooler and ofcourse an intake which would both maximise the gains if you went above stage 1
Sounds like they don't know what they are talking about if they've only done a stage 1 map to your car and now say there is nothing left to do
Click the search button to check out lots of threads on the possibilities of what you can do and whats needed at each stage of tune
HTH
Dave