Holden Colorado Engine Problems

You say it’s new, but not how many kays it’s done. I would wait until it is properly run in before doing anything rash like fitting an aftermarket chip. While they can improve the economy and performance as you say, fitting the chip would void your warranty on the engine and the drivetrain. If you are concerned about the performance first consult your dealer.

It's under warranty, so take it back and demand they repair it, the dealer's advice is rubbish.

You should take it back to the people who installed the gas system, as something is amiss with it.