Is it worth exposing a 4000 to the stream that has an AVR(CAM). It sounds like the ECM modifies the receiver, which will require the TSOP to be rewritten. The 4000 does not have a JTAG port, is there another easy way to read/write to the TSOP? Should only receivers that have JTAGs be used with AVRs?

When the next ECM hits a AVR(CAM) can the CAM be modified by the ECM? Can an AVR write to a CAM?

There is no easy way to read/write the TSOP on any receiver without a JTAG port. You can try locking the TSOP, but on some models you'll get nagged. Use'em until the won't work anymore... then replace with a cheapy 2700/3700 (or even the 301).

Nobody knows what an ECM can/will do... until after the ECM.

Cheers to ya!