I've had a 1" lean to the passenger side ever since I had my suspension components installed five years ago, and tried the usual cures by rotating springs, and even had TeraFlex send me a complete replacement set....but nothing seemed to help.
Let me say that the fuel tank has nothing to do with the problem....nothing.
The solution was to add a TeraFlex 1" spring spacer at the front passenger side, which cost me all of $20.00. This corrected the problem in front and back, and now my jeep sits perfectly level.
I considered installing adjustable sway bar links and making the passenger side longer than the left, but TF said this would create a preload issue and advised against it.
The reason I dispute the fuel tank as a source is that after installing the spacer, here are the measurement results using the left and right door hinges as a measurement point.
Empty fuel tank after spacer install: Left side 48 3/8".......Right side 48 7/16"
Full fuel tank after spacer install: Left side 48 7/16".....Right side 48 5/16"
These measurements were taken at the exact same place in my garage and the numbers don't lie....fuel tank has very little bearing in how my jeep sits.
These spacers come in different thicknesses, so I recommend this as a cure to anyone having the "gangsta" lean.

 

You didn't do the rear? I'm waiting for my front and rear to arrive. I was going to do both, what's the thoughts? I ordered 3/4 spacers, that's the height difference on mine.

 

Mine sets like that terribly.. Only i have rubi springs and a 2.5 inch spacer lift so idk what to do. Any ideas?

 

Had same problem! And teraflex even sent me new coils shocks and the spacers. So I did that with the soacers and it worked fine but then I put adjustable track bars and it sat unlevel again so took the spacers out and it has been fine ever since. So basically the problem is the trackbars...

 

I had a similar experience, 1 1/4" lean to the passenger side measured at each side of the rear bumper. Since I had a 1" Teraflex rear spacer on hand I installed it... and amazingly it had almost no effect on the lean. One clue was when I jacked the Jeep up dead center on the rear differential till both tires were off the ground and measured the rear bumper height again, lo and behold it had the same lean to the passenger side even though the rear springs (gas tank and all) were out of the picture. When I checked closely I found I had miss-adjusted my sway bar links, that accounted for 1/2" of my lean. I then installed one additional stock 3/4" spacer(free thank you Jarad @ ORW) on the front passenger side and "Bingo" no more lean

 

Terraflex 4" lift passengers side rear is 1" lower

 

I have all my work done by a local shop called Desert Rat here in Tempe AZ. The were set to install spacers on the front and rear passenger side, but first tested by just doing the front....which is all it took to get my jeep sitting perfectly level.
Go figure????

 

You mention that installing the rear spacer had no effect in correcting the problem, but when you installed the front spacer it fixed the lean. Seems to me that the cure always relates to adding a spacer to the front.

 

I suggest contacting the manufacturer of your lift, or the company that you bought it from and see what they have to say. I doubt you can add an additional 1" of spacer lift to the front right side, but I'm not an expert....just know what worked for me.

 

Reading this post re affirms what I have been saying all along. Teraflex is a fantastic company.