When I hit 3rd gear in my 87 YJ if I press on the gas to get it up to speed for the next gear I hear a clicking noise. I assume this is because I am trying to put too much gas into the system, but I will never hit 4th if I dont do it, I'll stay at about 40mph max. Is there a way to increase the amount of gas it can handle or is there something that would increase torque so I hit 4th with less gas? I have a 4.2L, 258 Straight 6 engine

look to see if you exhaust header is cracked