Good local shop for emissions issues? Non-SHO.

[nomov8sho]

Hey! I'm battling with an odd emissions failure on my wife's '91 Chevy Caprice wagon.

Can anybody recommend a good shop in Phoenix to troubleshoot this?

I posted a thread in general chit-chat starting with "OK smart folks-" if you want to see the specifics of the problem and what I've done so far.

Thanks,
-Josh