Metering diaphragms do go bad just sitting without use once they have been exposed to fuel. Basically they get stiff.
But first seat both mixture screws counting the turns as you go in so you can reset to the same setting. This may unplug the mixture port holes as I have seen them still plug even after cleaning. If this doesn't help try adjusting the L mixture a little richer ie 1/8 turn CCW and see if it stalls less as the unit may simply be running too lean at idle. This something I have seen several times after installing a new kit as the parts settle in, the adjustments change. It is one of the reasons I keep an unit for a few days after a carburetor rebuild.
Question. Is this Titan using a Zama or Walbro carburetor? The metering lever is set differently between the Zama and Walbro which why I have Z metering tool for the Zama and both W metering tools for the Walbro.
