What are outside temperatures when experiencing your concerns. If 70 degree 'F', engine start and initial performance will be dramatically different than at 5 degree 'F'. I will leave it to you to do the Celsius conversions.

The intake that you are running unlikely will ever give you decent cold weather performance or economy given its lack of crossover exhaust porting to quickly warm it up,,,and is unlikely to ever warm sufficiently for optimum economy.

In warmer weather you should not even need a choke to start the engine. The fact that you indicate that it is closed when starting the engine suggests that your poor performance is occurring in very cold weather. Hence the need for a rapidly warming up intake, which you do not have.

In warmer weather, intake manifold warming even without crossover or heat riser will be quite rapid,,,even with a single plane intake.

Your other option is to leave the choke closed for an extended period of time until engine finally warms up,,,,just not a good option,,,poor performance and economy and rapidly polluted oil and a likely more quickly rusted out exhaust system if you use for a lot of shorter trips.