I'm planning to use a 2.7L in a buggy build.  I'd like to remove the cats on the exhaust manifold and replace them with a single cat after the Y-pipe.  Since I may try to register this vehicle for street use at some point, I'd like to keep it complaint and not have the computer throw any codes.  My question is, can I combine the wires from bank 2 sensor 1 with bank 2 sensor 2 and run a single downstream O2 sensor?  Has anyone tried this or know if it will work?  Thanks for the advice!

I haven't tried it, but I'm fairly certain it won't work.

Anytime the ECU sees the same signal on sensor 1 and sensor 2 of the same bank it will set a catalytic converter "below efficiency" code

And I have found that when running with a code on the O2 system or Cat. system my mileage drops.  If efficiency drops so does power.
Why use the 2.7 when the 3.6 has more to offer at close to same price especially in a buggy.  And the ECM can be re-flashed to set your parameters.

I haven't tried it, but I'm fairly certain it won't work.

Anytime the ECU sees the same signal on sensor 1 and sensor 2 of the same bank it will set a catalytic converter "below efficiency" code

Thanks. I realized that I had my info confused in the initial post.  I didn't mean wiring sensor 1 and 2 of the same bank together,   I meant wiring both downstream sensors together.  so that would be bank 1 sensor 2 and bank 2 sensor 2. 

Another option would be to weld bungs for put both sensors next to each other downstream of a single cat.  But that may raise some eyebrows in an inspection, which is why i was trying to avoid it...

Why use the 2.7 when the 3.6 has more to offer at close to same price especially in a buggy.  And the ECM can be re-flashed to set your parameters.

I already have a sidekick doubler and toyota transfercase w 4.0:1 gears.  i wasn't sure what the tranny/ tcase options were for the 3.6, so I didnt really consider it.  I was originally planning to use a 2.0L that I already had, until I found out the 2.7L used the same t-case and my sidekick doubler case would bolt up to it.

Thanks. I realized that I had my info confused in the initial post.  I didn't mean wiring sensor 1 and 2 of the same bank together,   I meant wiring both downstream sensors together.  so that would be bank 1 sensor 2 and bank 2 sensor 2. 

That might work - I'd be inclined to try it with a couple of diodes wired in to provide isolation between the two inputs - the problem with that would be the voltage out of the O2 sensor is quite low (approx. 1 volt) and most diodes have around a halh a volt drop - there's a guy goes by the name of rhinoman who is something of a guru with Suzuki ECUs - he runs a forum over at rhinoman.org - ask him about paralleling the downstream O2 sensors and hear what he thinks of the idea.

Another option would be to weld bungs for put both sensors next to each other downstream of a single cat.  But that may raise some eyebrows in an inspection, which is why i was trying to avoid it...

Inspection?  I assumed a buggy build would have been off road only, and no inspection required.