1998 Toyota Tacoma CNG Hybrid 2.7l 3RZFE 2WD regular cab pickup truck

Reliable little 1998 gem. Toyota Tacoma base model regular cab pickup truck. Converted to CNG back in 2008 when gas got really expensive. I have too many vehicles and this one doesn't get used as much so it's moving out. CNG system is a fogger type that shuts off the fuel injectors when shifting to CNG fuel. CNG then depressurizes from a regulator and then is piped into the throttle body bypassing the air intake and going directly into the cylinders. CNG combustion temperatures are significantly higher than that of unleaded. Consequently, CNG vehicles (unless factory CNG) need valve maintenance every so many years. So after the 2nd valve job, I installed a new motor head (about 117,000 miles) so the new motor-head has roughly 26,000 miles. The machine shop that built the motor head gave me the option of valves to retro fit with. I opted with hardened valves. The lead machinist speculated the valves are made of tungsten carbide because of the difficult time he had grinding the valves to specified parameters. So theoretically this motorhead should be fine for a long while before needing any attention. I tried the CNG system out a couple of weeks ago and it works fine. I've only had issues when operating in cold weather conditions. Recent work done:
-New paint job by Maaco
-Brand new tires
-Brand new catalytic converter
-Fresh upholstery shampooing
-New floor mats
-New Windshield
-New battery
-K&N air filters (intake and cabin)
DISCLAIMER!! This is a 23 year old vehicle. Although I have done my due diligence in maintaining it, there is no warranty expressed or implied. This vehicle is sold as is. It has been an extremely reliable little pickup truck and my hope is that it will be for the next owner as well.
The following link is a tutorial on filling and funtction of the natural gas.check engine light in the video was a result of code p0420 meaning the catalytic converter was past it's thresh hold limits. I tried burning it with fuel additive but it did not work. When I removed the catalytic converter to clean it, I simply decided to replace it based on age and condition. The code has not returned.
Any other questions please don't hesitate to drop a line.

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