n/a is a little different to turbo.. you couldn't interchange chips on a turbo motor and expect it to run nice.. the chips in the n/a motors though, you're pretty cool for most anything.. within reason of course. things excessively high compression you'd need a different tune.. i've done extensive testing on running the stage 3 chip in a motor with stock intake and exhaust.
basically the stage 3 was tuned around having a cam, exhaust and intake, headwork etc. but has been tested on a variety of configurations succesfully. you just want to make sure you run at least 95 octane, but i'd recommend 98. you should get more power out of the stage 3 than the stage 2 on any configuration. the stage 3 has more agressive timing and a leaner, more linearised (smoother maps) fuel map than the stage 2 chip.
linearising the maps tends to help with achieving more torque and smoother throttle response. the stage 3 is tuned to run 13.3 - 13.5:1 air fuel ratios right through the rev range (except cruise/idle which is leaner) the stage 2 chips run a bit richer and are not linearised, they also run less timing.. this allows people to run cheap (non premium) fuel and not experience pinging. there is of course a chip i've developed that runs stage 3 maps and less agressive timing which is good for regular unleaded.. i guess you could call it stage 2.5 if you really want to confuse people.
the stage 'x' for the antrx chips (and most other chips) is basically just a branding to differentiate between different levels on tune, recommened (on n/a) for xx mods, but not actually required to have xx mods. i've more so based it around what fuel you should use. stage 1 (discontinued) was just a very basic chip, performed better than stock, but could be used on any fuel. stage 2, 95 octane is recommended, but has been sucessfully run on regular.. stage 3 is for 98, but has been tested on 95. each stage should offer more power than the previous.
turbo tunes, i always recommend a custom tune.. and i'm more than happy to do this.. it doesnt cost any more than getting the chip of the shelf and i can gaurantee you a far better result.