All you need to do is get a new orfice. NG is about 1/2 the btu output of
propane so the orfice should be 2 times as large. There is a bit more to
it than that so just reaming out the current orfice will not get the
desired results. These changes usually cost about $40.

I took the 5 burner manifold from our "Aussie" grill into the local BBQ
shop and they drilled out our 5 old orifices to a larger size.

See your local BBQ dealer.

Thats who did the job..works fine

R