Have never really tried CNG on a Civic Prosmatec but I would imagine that with proper tuning it would give decent performance.
On a 2005 City Auto, we had some strange issues with the AC on, the car would at times just stall and the brake would also become hard, furthermore the CNG performance on that car was just bearable. I am not sure if it is a model fault or that particular car. In my experience, there can be significant car to car variations across the same model on most Pakistani assembled makes.
On Corolla 1.6 and 1.8 models that we have owned (both autos), the performance is quite reasonable however there is something that needs to be done inside the engine after around 50-60,000 kms(valve replacement and head grinding) to keep things rolling. Cost us around 20k and was required on both the cars. Even on manual transmission I know of another 1.6 that sort of had an engine breakdown at about 110,000 kms. I believe the 1.3 xli is the most CNG compatable engine.
CNG kit vendor and tuner are obviously both very important people in the whole equation, I have been going Raja Ustad on Sarya Chowk in G-8/4 Islamabad for over 20 years now... yes that stretching back to the LPG days!
Nevertheless, I wonder if there a reasonable way to change ECU settings to make the more high tech Honda/Toyota engines more CNG compatible? Moving to a programmable chip may be one solution but costs are probably too high.