ls/200r4

[D-adams]

I'm needing some help please. I have a 1972 c10 that has had the 5.3 with the 200 r4 behind it for 6 years now working wonderfully. This spring I pulled the motor and done a cam swap and upgraded the stall converter. I sent the ecm out to get tuned and when I got it back it will stall out every now and then now. Mainly coming to a stop sign or backing up. When I hook my scanner up to it, it says its in 3rd gear when its in park. I also noticed since the ecm has been tuned that my speedo on the dash works but my electric speedo I run off my OBD2 does not. Could anyone tell me what tells the ecm what gear the tranny is in? The tuner believes the ecm is cant adjust the rpms for what gear it is in because it dont know. And iIm not sure why I all of the sudden dont have a working digital speedo.