Self tuning Khyber on CNG & problems faced..

I have a 1998 Khyber G10 engine with tartarini kit & 50 KG cylinder.I have a little knowhow of tuning.My car is giving 165-170 KM on a full cylinder without A/C. I decided to carry out little tuning / inspection myself. I did tuning in following steps:-

1. Changed air filter, drained oil from CNG regulator.

2. Opened Denso W-20EX-U plugs, inspected, cleaned & adjusted gap to 0.75 MM.

3. Took compression of cylinders, it was around 11.8-12.1 kg/cm2.

4. Fitted back plugs as per mentioned torque.

5. Started engine on CNG. Warmed up engine. Opened tappet cover, adjusted intake valve clearance to 0.25 MM & exhaust valve to 0.28 MM.

6. Fixed timing light. The timing was 8 deg BTDC with 1000 RPM.

7. I decreased the RPM to 850 RPM with carburator air / fuel mixture screw.Then changed timing to 4 deg BTDC as per workshop manual.(My car is without advancer)

8. I felt decreased in performance so i again changed timing to 8 deg BTDC since i usually drive on CNG.

9. Now, i m facing following problem.
a. Veh is giving good starting on cold engine. But it is taking 5-6 seconds self on warm engine.Acceleration & performance is OK otherwise.

10. I have following questions from CNG gurus.

a. On CNG, more air is required or less air as compared to petrol??

b. While tuning on CNG, RPM is adjusted from air / fuel mixture screw on carburator or from the screw located on kit(regulator)?

c. Where is the small cng filter loacted in CNG solenoid. ( I read it on tartarini website that a small cng filter is located in cng solenoid).