2010 Mazda 3 1.6 displacement manual. Losing momentum going uphill.I am a car lover. I'm in China, this 2010 1.6 displacement manual transmission Mazda 3 (made in China). The vehicle is modified with natural gas, and the natural gas device is South Korea's DYMCO. I replaced two sets of spark plugs for this car (DENSO fk16r11, NGK VW AG) 101905611G), lost power when driving on a steep road with a gradient of about 26.57°,50%， and a length of about 60 meters, the engine speed is 1st gear 2000-3000 rpm without power The car is turned off, 4000-5000 rpm has power (steep mountain bikes switch to gasoline, no natural gas). The engine is fine, I think the spark plugs are not good. What type of spark plugs are installed on the Mazda 3?