I have noticed a problem with my 97 TJ not gaining any speed on 4th gear at 55-60mph and a significant decrease in my gas mileage. I took it to my mechanic to see what the issue was and he stated that my catalytic converter was producing excessive heat, restricting my speed and affecting my gas. My catalyst was just replaced with a magnaflow in Apr of this year. I feel like that the problem is just more than a bad catalyst and something else might be going on with the engine. How do I go about telling my mechanic to do some further testing without making it seem like i'm stepping on his toe? This is a matter of having to spend more money for a new catalyst if the problem is with my Jeep. Thanks in advance.
97 2.5L TJ
RC 2.5" Lift w/ Bilstein 5100 Series Shocks, Adjustable Front Track Bar and Rear Bracket, Steering Stabilizer, 33x12.5 Duratrac, Cragar Soft 8s, Magnaflow Cat Back Exhaust and Catalytic Converter, 6-spk VDP Soundbar, Rampage Frameless Top, Kargo Master and Safari Roof Rack