The MC34063 is used as a boost converter and is already boosted with an NPN transistor in case of loads although Vtuning doesn't load it, it's powered from the arduino VCC, it supplies +30V (5V in 30 out). The TA2003 receiver gets signal from tuner IF through the SAW filter and a coax cable (sorry not illustrated in the schematic).
The 10k pull up resistors are in fact 4k7 to my surprise and make no difference when added or omitted. I tried the SN761672A tuner and the TDA6405A, the setting is almost similar. I even tried more than tuner with the SN761672A and new ones (I got them very cheap). I have the feeling something in the code, say, the timing or intervals for the bus and the signal to set and rest????!!!!