Update...replaced air filter, broken breather hose, replaced some of the old vacuum lines for the peace of mind, still no start when warm. Went the electrical route... checked plugs, wires, cap & rotor....found the rotor to be very worn & rusted, replaced it with another used one I had in the bin, but in much better shape. Result...no warm start issues for last 2 days, we'll see if it is a permanent fix in the next week or so...