There are things he can perform at home
1. air filter change, (10mm socket required)
2. throttle body cleaning
3. spark plug change/clean, (16mm socket, required)
4 ignition wires resistance check, (multimeter required)
These tools are not expensive as compared to paying mechanics on each visit. These are simple maintinese routines, and tons of youtube videos can guide him.
Then comes tuning of fuel system. I am personally using STP complete fuel system cleaner and satisfied with its performance. Change the fuel filter after that. This also can be done at home.
Finally for total conversion from cng to petrol,
1. In factory fitted cng cultus, there is air blockage inside somewhere in between air filter and throttle body, can't remember exactly where it was as I removed it long ago, and never drove mine on cng.
2. Distributor timing is kept at advanced for cng, it can be brought back if no further cng is being used.
He can't do this at home. An expert mechanic can do this. https://www.pakwheels.com/forums/t/cam-setting-through-distributor-positioning/426788/9
3. And finally is tappet adjustment. Both of these, distributor adjustment and tappet adjustment shouldn't cost more than 500. It's a simple work but requires some experience.
That's it, should be an economical car.
