You have the 'toaster' burner, and if you have orange flame on one side, this indicates that your burner is not level. You need to remove the top baffle and the burner shells. Remove the wicks, and check the level with a spirit level, both lengthways and sideways. Ensure that the legs are in the recesses of the cooker base. Then open up the oil flow and let the oil fill . After approx. 10-15 mins, check the depth of oil in each of the channels. it should be the same at both ends of each channel. The oil level depth should settle at 10mm throughout the whole burner. This is where the level is important. If your level is too low, then adjust by screwing the legs in, but ensure that you maintain absolute level of the burner. Once you are satisfied with this, replace the wicks and burner shells ensuring that they seat fully on the base, then replace the top baffle. As the boiler is ok, do not adjust the float control height to correct the discrepancy.
To check flow rate, you need a calibrated measure, into which you allow the feed pipe to drip over a periodof 2 mins . Divide the volume by 2 to get the 1 min rate, which should be 13cc at high fire.
Once all this is established, you can check operation using the manual lever to see if you get good constant flame. One other thing to check is that the flex-a-temp is opening up the control pin fully. after a couple of mins, there should be a discernible gap between the operating arm and the pin.
The other factor to check once it has warmed up is to check thermostat operation with an oven thermometer at the switching point.
Vapourising burners are simple. Do the simple things right and they will work.