no matter how many times i say this, people will NOT listen...
putting sticky tape over the air intake DOES NOT improve performance, it DOES NOT increase mileage, it DOES NOT increase pick, it IS NOT the proper way to tune up a car!!!
putting sticky tape over any place in the intake only serves to choke the air intake and reduce air supply
less air requires less fuel to burn
less fuel+air mix gives less power for any power cycle
less power means you'll end up pushing the car more to attain desired speed
and pushin it more means less drivability and less mileage!!!
Besides, if ur cng mixer is installed between the throttle body and air filter housing then you should be fine anyway. Enough negative pressure is generated to get the cng sucked in.
lesson for everyone!
if your car has to be duct taped at the intake then your mechanic is probably trying to dupe you and MASK the problem rather than solve it. Period.