Came upon this thread as I was having similar issues. Currently running bilsten 4600 with stock springs on a 2001 T4R with a MagnaFlow Overland Series Cat-Back Performance Exhaust System #19538. The lateral arm bolt of the lateral arm from the rear axle bangs into the exhaust system upon compression and it's starting to leave a dent (just like the OP). I had it installed at a shop and wasn't sure if the exhaust system was designed with a lift in mind or if the shop can adjust the exhaust to avoid the bolt. Anyone have the same experience?

Haven't had time to take it back to the shop to adjust since it's my only vehicle and I need it to get to work.

Thanks in advance.