I have been participating in RC car racing for a considerable amount of time. Recently, I began racing off-road on carpet tracks, which has proven to be quite difficult. Despite using a tuning sheet for carpet tracks, I am still experiencing issues with my car feeling loose and difficult to control, especially during turns. I am currently using a Fly Sky nb4 controller . Wondering if adding a thicker sway bar will help? Thanks

Can we assume that you are running a gear differential?

I am running a 2 gear with 65000 grease .

What type of carpet are you running on and would you be able to post your current setup as it would help people advise which changes to make?

Lots of potential issues.

Swaybars are important.
If your carpet isnt high grip, may need to treat it more like astro.

There are a ton of setup sheets out there for a b6.3 and 4. I'd grab one from petit or ae and start there. Get as close as you can, ideally with everything matching except for the chassis. Go from there.

Also
Turn your servo speed down.
Use negative expo

Carpet is very different than dirt tracks. Even modern “dirt” tracks for 1/10 in the US are very different than they were back in the 80s. “Feeling loose and difficult to control” probably needs a bit more detail. Generally a car will feel looser on real dirt tracks as it fights for grip. Carpet is such high traction it’s not typical for the car to feel loose, but often the opposite as twitchy. Twitchy can be difficult to control and cause you to over control the car causing traction rolls. The difference of on and off-power steering is very different for carpet than on lower grip surfaces for 2WD. So where are you feeling the difficulty with your car?

Also make sure your tires are good. Carpet tires can look ok (have tread) and be terrible with no grip. So grab some new tires, if it doesnt fix your issue take them off and save them for after your issue is fixed. Tires will always be used.

Also make sure you dont have any bend or binding suspension. Take your shocks off and make sure your suspension falls under its own weight and freely moves.