Ok so I've just pulled the ECM codes from my 94 Blazer before I started looking for a possible FPR problem and I came up with code 83.

I had a look on http://www.troublecodes.net/GM/ and see that the generic fault for code 83 is "TCC solenoid circuit fault" but I also noticed that in the specific list for my year and vin 83 wasn't listed as a possible option.

Could I have a later ECM swapped in or something?

When I've finished checking for the FPR problem I'll reconnect the battery back up and see if it reapears.