I have a similar situation. I just added a Toytec 3" lift to the rear of my '99. These coils #9602RC-P are side specific, as the driver's side coil is markedly taller. Also, the coils are marked 9602D (driver's side) and 9602P (passenger side). Look at the attached phots to see what I'm talking about.
When installing the coils, I was very careful to get the proper coil on each side. If you can read it in the image below, the number is 9602D, and the photo is from the driver;s side of my truck.
After the lift (rear only, so far...ran out of daylight), the passenger side is a FULL INCH TALLER than the driver's side! WTF???? I was careful to clean the perch for the coil, as well as to seat it properly, so I'm at a total loss here. I will give Toytec a call tomorrow, as they are closed today (Sunday). ALSO-the front is still stock height..could this be the problem??? I don't see how.... Dunno.
Thanks,
Jaime