There are many good products on the market that will clean fuel system " as
you drive " A slightly clogged injector, or gummy carburator will respond
well to these treatments. A jammed shut injector, or filthy carburator
won't flow well enough to noticably improve.
I'd say cleaner is a good idea, I'd change fuel filter after burning up a
tank of treated fuel, just to be extra safe. As for "cheap" gas, I doubt
the EPA would allow the sale of truly bogus fuel. Some mechanics say cheap
gas burns up valves. I use cheap gas, and have yet to have any problems.