What causes 2 identical B44's to be so different?

[Team No Idea]

I think im going a bit mad..... it could all be in my head.
Ive been racing my B44 indoors at FORCC for about 8-9 months and gradually getting the setup as i like it.
over the last few months it really has felt spot on and im mega happy with it. However the outdoor season has kicked off and i have been very reluctant to disturb the settings each week to go and do the regionals.
So now i have purchased another B44 to use indoors only. It was second hand, a few weeks old and i have completely stripped and re-built every nut and bolt so it is identical to my other car.

However it handles sooooooooo differently to my 1st car, the rear end has a mind of its own and its nowhere near as confidence inspiring.
Could this simply be the various tiny manufacturing tolerences that make a difference? should they be the same? is it normal for 2 cars to be different although setup the same? soooo many questions! lol looks like iv'e got to find a completely different setup to make this work....

Any ideas?