I've struggled with my B4.2 since I moved to 2wd after driving 4wd SCT for the last 3-4 years. I'm running in a 17.5NR class on a high traction outdoor track. The car always felt nervous and at the same time seemed slow in some corners. The local top dog regularly runs faster than 99% of the Mod guys so I asked him to check out my car and make some suggestions on my setup. He gave me a couple changes to try and then drove it on the track. He asked if I had ever tried a full sized pack. So I threw an old NanoTech 5600 in the car and could tell that it was easier to drive, but I couldn't tell if it was faster. First round I wound up TQ (fast guy was just practicing indoors) and a full lap faster than I usually run.

So, if you're struggling with setups and a shorty pack try going back to a full size. I'm back to the stock setup with White/35 front and 32.5/Green rear. I'm running a Reedy 309 (318g/7000mA/65C) pack. Besides stabilizing the car the pack holds voltage better than the shorties I've tried.