Generally, if you go the full setup, you will need a tuner of some sort, where as you can get away without one with most slip ons. That was what the local stealer told me anyways.

I think you will find that slip on's give the better performance over a full system by keeping the OEM headers. If you just replace the mufflers you can get away without a tune. Once you go to A/C then the bike will be sucking in a lot of air and will be lean. OK for a short time but you will do damage to the engine over a longer period. The ECM can only adjust a very small percentage for the AFR 14.68. Changing both sends the requirements outside the ecm's capability.

mate, just shell out for a full system ....

if you go slip ons now, you'll be changing to a full system before you know it