My MAC's had to extend the o2's, i'm sure BBK are the same.
The reason is location of the boss in the collector, as opposed to the h-pipe.
To keep from burning clutch cables get the heat wrap(about $15 i think??)
A foil looking sheath to slip over the clutch cable.
No, the smog doesn't have to come off, but i took mine off(lots more room)
Also, i didn't get a kit to extend the wires, just took wire, spliced in new, soldered, and taped up.
Did it 3 years ago and no problems at all.
If you do leave the smog, you either have to cut a hole in the h-pipe to weld in the tube,
or use a catalytic h-pipe(it should have the hookup)
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4.10's,long tubes & 75 shot...Goes 12.50's
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