Cadillac Repair: Fault Code, transmission treatment, transmission shop

Question
My 99 seville has been running pretty bad for the last month, it would seem
that on occasion I was running out of gas but it would never die and Id have
plenty of fuel. As time went buy the occurences grew more often and the car
began to backfire. I replaced the fuel filter as it swas an easy job and I was
convinced it was fuel related. Of course this changed nothing, I have since
used the DIC to run codes and got the following P1520 - (Transmission Purge
Circuit) and U1064 - (Loss of ccommunication with DIM)

I am at a loss of what to do now. Please help. Refer to http://
www.cadillacforums.com/forums/northstar-performance-technical-
discussion/94070-99-sls-runs-funny.html for a spread I started to work this
out.

Thank You very much

Skott

Answer
How often does it do this, when its hot or cold? Are you trying to accelerate when this happens? what happens if you rev the motor up when its warm and in park? what happens when you give the motor hard acceleration in drive? and is the a/c on when this happens? i need to know those[basic] things before i can try to diagnose your problem. I would also take it to a transmission shop, or put lucas transmission treatment in.