My '13 access cab V-6 auto, with stone stock
had a 1/2" lean at the left front and 3/4" lean left rear. This is with less than 4000 street miles. I put a 1/4 " shim (lean spacer) on top of the strut. This brought the front very close to level. It also helped the rear a little. The rear still leaned 1/2" so I installed a 1/2 " shim plate to even out the rear. I got this plate from streetacos.com. It bolts to the bottom of the leaf pac and comes with a new spring center bolt. They sell 1/4, 1/2 and 3/4" plates. The stock U bolts are just long enough for the 1/2"plate to fit.
I wouldn't call what I did a lift, but the truck sits a touch taller and looks much better.
What I am saying is the stock springs DO lean in most cases, most often just the front, sometimes the front and rear, and almost always to the left side.
I have heard that Toyota corrected the lean using a different left and right spring, but you couldn't prove it by me. I've checked many 2nd gen tacomas, mine is not the only one......