Most of the off roaders have upgraded to metal gears. You can change your gearing to change speed vs torque but make sure not to get too high for off road then your motor will work more. Try a slight gear change in plastic if you don't like it not so much $$ involved.
Is it really worth it to have 2-speed though ?... not money-wise but the hassle of having it. I read a few threads on the issue but it seemed to be more people prefer not having it. Some really like it though. So that leave me undecided for now until I read more about it.
If you already have the torque engine(29cc) you probably have enough power off the line where you can stay at a single speed and upgrade to a 20/44 combo. This will give you the top end you are looking for.
A 2-speed is a lot of work to set up properly. You need to find a first gear set that gives you the accelleration you want to mach your low to midrange powerband, then you find the the second gear set that gives you the top end your motor can deliver. Then you fiddle with the shift points so the transition between the two is smooth and in the powerband (on the pipe), you don't want the motor to fall on it's face when it hits second gear. You get this right and you will have a road rocket with the power down low in the corners and accelleration on the straights. Now you change tracks or do motor mods and you start all over. Look into any racers pit box and I bet you will find a drawer of gears. I have many drawers of gears. The biggest misconception on 2-speeds is that you throw them in and your faster. If you are willing to do what it takes to properly tune it to your equipment/track it will be faster, if not you won't be happy with it. You can also accomplish the same result (and cheaper) with the stock pinnion/spur set but it is not as fine tuneable but good results all the same. Just change a few teeth at a time untill you find the right balance of low and top end for your setup. The down side of the large scale cars is that the motors are not moveable so we have to purchase matched gear sets and there may not be as many choices unlike the smaller scales. Have I thourally confused you yet?