‘05 T100 Slip On Question

It depends which slip on you are going to fit. The Triumph off road pipes could be fitted to the 865 motors without changing the jets. The 790cc engines needed different jets.

As far as other makes of pipe are concerned I do not know.

Many years ago I had a 2005 T100 with Tors pipes and more recently a 2006 T100 which I bought with Tors pipes fitted and neither needed different jets.
On a personal note I did not like the tone of the genuine Triumph after market pipes and my current 2006 T100 is back to running on standard exhausts.