I have the GT, the same as your SP, but in the UK models before 1992 (mine) had 104 kw (140bhp) and 1992 onwards had a cat and therefore only had 92kw (129bhp).....
And bourbon was refering to exhausts affecting performance coz of the cat, not slowing the car down.
And i don't think the BA has more power than the BG.
The Cat BG's had 129bhp, whereas i believe the BA's had 118bhp...... in the UK anyway.