How many turns out are your idle screws? Should be about two turns for a 34ICT. If it's more than that, the idle jets are too lean. Most of your driving is actually done on the idle jets and the mains don't kick in until 2500RPM up. That latter range varies depending on venturi size and how many cylinders are being fed by the same venturi. I wouldn't go higher on the timing just yet. Another question, do you hear any pinging when you accelerate at low speed?