3.5 rough idle

[Old 3.5]

I have a 1995 concord that has a ruff idle and will not pass emissions test Also gives no code. Why no code if it failed emissions? One shop says throttle body is leaking at the shaft after they used smoke to find vac leaks. Idles ruff and smells like it is running rich at idle once motor is warm ?
Is this a known issue? They also said one ox sensor was giving a high reading and the other one was low reading . Both ox sensors where replaced about 5-7 years ago.
I would like other opinions before I spend more $$$ on it.
Has Around 157,000 miles no smoke, newer plug wires. Also sprayed mist on wires at night to check for arching saw none.
Had the intake manifold gaskets replaced last summer with no improvement!
Gas mileage is good at 20 . Other wise engine runs very good in every day driving! My parents bought this car new I got it in 2005 so it has always been well taken care of. What do you think?
Ps: if it is leaking throttle bodies I found a on line auto parts place that has only a few left for 80.00 each pass and drivers side. Or are they rebuildable?