Paul,
The only guy that I personally have experience with is Jim Inglese and his shop is in Lake City, FL which would require removing the intake manifold and shipping it back & forth. If the setup just needs tweaking that would probably be overkill. But if they have some years on them and haven't ever been properly set up before, he could go through them and make them right for that application. When he sends them back they are ready to bolt on and make final idle adjustments and go. He would also be available to follow up with you when they were reinstalled to help you get them dialed in right. (And no, this is not a paid advertorial!)
However, if they were running right recently and have been gone through within the last decade it might be best to find someone local to trooubleshoot or tune them.
You do not say which engine these are on and whether it is running a cam optimized for Webers. They are a decidedly different animal than a traditional plenum manifold and require a cam that is designed to work with individual runners to get the best results. It's my understanding that almost any Weber will work at idle and wide open throttle at RPM, it's the 1500-3500 RPM range where they need to be set up correctly or they will stumble. Your friend's car sounds like it's running rich. If it was lean you would hear 'popping' through the exhaust.
To set them right you'll need an airflow meter and a couple different sizes of jets (there are three different ones; main, idle and air corrector). These are initially selected based on the engine and engine mods, so if these carburetors came off a different engine, that could also be problematic.
The good news is that once dialed in they work great for a long time!
~Kevin