See, understand this principle, and you will never have a problem.
Patrol is liquid and it is supplied to the engine via pump.
CNG is gas, and it is delivered to the kit by it's own pressure and then sucked in the engine.
To improve the engine's "sucking" you need to block the air intake about 70%.
Because Pressure is inversely proportional to area in this case.
Once you have placed the piece of cardboard, the engine's starting should improve as should power.
After that you will need to adjust the mixture ratio and the car's timing.
Enjoy !