If you add a T/A and phb then you will not need UCA.
A phb will help in cornering but won't do anything in the 1/4. All it does is help
locate the rear axle in side to side motion. The Torque Arm will help in the 1/4, how much I don't know. The T/a will help with axle wind up, meaning it will allow the rear
axle to apply more power to the axle's, instead of the axle housing rotating slightly before it applies full power to the tires like in the stock suspension.
I just installed a MM phb in my car a couple of weeks ago, and it makes a MAJOR difference
at initial turn in. The stock suspension bushings & control arms allow a little play to prevent bind, thus allowing some side to side movement and in turn allowing rear stear. With the phb it virtually does away with all side to side motion and allows a smooth transition from straight away to cornering. Just be careful of exhaust clearance when installing the phb, if your not careful you will have some contact between the phb mount and exhaust piping (i.e. rattle). And MAKE SURE you have a good drill and drill bits (several different sizes) to make it through the frame rail. Also be careful of what kit you buy, some phb kits will bolt to the floor of the trunk, thus allowing flex and defeating the whole purpose of the phb. Make sure it bolts the the frame rails.