Is a rear sway bar needed with my setup?

Why would you disconnect the sway bar for street driving?

If it's a street car then you should have the sway bars connected. If you have swapped the front sway bar then you need to ensure that the rear sway bar is a match for the one that you've installed in the front.

You can get undesirable/unpredictable results when you start messing with the sway bar setup. Your rear sway bar should be designed or at least a decent match (1/4 to 1/3 (roughly)) larger than the front.

To ignore the relationship between the two will NOT improve your street performance. The only reason I can think of for you to disconnect the front sway bar for an advantage is because you're at the drag strip with a set of 90/10s in the front and want as much rise for the front end as you can get to ensure weight transfer to the rear.

Hit a hard corner with the front sway disconnected and it will understeer like a big dawg (you turn the wheel, the car goes straight) or you overpower/bottom up your strut and see the ass come up to meet the nose. Neither of those is something that I'd like to have.

Hitup MFE92

I'm sure he can explain better than I can and I KNOW he understands the characteristics better than me.

If it were me, I would keep the stock ones until I had figured out what my requirements were going to be.