Carb set up
As I have asked in this post before what are the venturi or Choke sizes you are using.
You can have great bottom end and off the line starts with a small venturi. This will also give you fairly good fuel economy. Be careful as it is possible to go too lean and run the engine too hot. I have seen the exhaust ports start to bleed aluminum droplets.
So the basics are as follows small venturi great bottom end and off the line starts with good fuel economy, the engine will starve at higher RPM's. Larger venturi's require larger jets, have poor bottom end but great top end, poorer fuel economy.
You need to always tell us what venturi size you are using, what main jet and what air correction you are using. The idle circuit is totally different. If your carb is set up correctly you can remove the emulsion tubes while the engine is running off of the idle circuit. If you remove the emulsion tube and the engine dies then your throttle plate is opened too much on the stop and you are running partly on the main fuel circuit. Correct this. You can also change the accelerator pump jet as well to prevent stumble when punching the gas pedal.
So let us know what set up you are using, idle jets, main jets and air correction jets. Then we can arrive at a solution.
One other thing. All stock Fiat engines were under carburetted for emissions reasons, the stock cam will restrict flow just above 5,500 rpm. So cam timing is also an important variable.
TonyK.
Grimsby Ontario Canada.