From what I've heard any turbo muffler like dynomax is ok, just stay away from flowmasters. I believe Borla makes a good 2.3 muffler - I've heard them on XR4ti's and they sound really good - not too loud.
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Mike
'88 5spd TC
'87 5spd XR4ti (in shop, rear ended by dickhead in 98 VW Beatle)