I have no experience with the TM flatslide carbs on a 350, but based on experiences with the VM series, almost every internal will need to be "adjusted" as the Mikuni's usually arrive set-up for 2 stroke engines...... Slide cut-away and needle will often be "wrong" for your application, jets will likely be too "fat" and slobberingly rich, etc, etc......
Someone who understands the Mikunis may eventually arrive at the correct assemblage of internal parts, (after significant parts swapping and expense) but then will also be dealing with the larger porting which was engineered for the CV carbs the bike came with....... The later model SL 350's had much smaller intake porting to match them for the Kei-Hin slide valve carbs that were used......
All that effort and expense will produce an engine that is not appreciably "better/stronger/faster" than the original set-up and carbs unless the engine internals were also "upgraded" (larger valves, more radical cams, higher compression, etc)....While this might be desirable for a race bike, it becomes a detriment as to "streetability" and operator comfort...
