I had a VATS problem for a long time with my 92 Z28. I ended up buying a PROM VATS bypass chip (you insert it between the ECU and the PROM, 10 minute job) and bypassing the starter enable relay. I had to go through all that because even with the correct resistor the VATS would randomly keep my car from starting (something was probably wrong with the wiring/ECU). Anyway, if worst comes to worst and even with the correct resistance you're having intermittent trouble, that's what you can do.

 

Heck sounds like ya have maybe like prev suggested a dirty/coroded terminal or connection somewhere in maybe the starter area.As for the vats system Q yea if the vats reads wrong resistance basicaly you will get nothing at all.Turn key and nada.Starter no turn nothing.I would wait about 10 min b4 trying again.Remember the res table shows max & min tollerances allowed for each key.This means you do not have to get the res perfect.Also if you have to use more than 1 resistor to get the proper value run them in series one after the other like this ( ------- ) not paralel side to side like this ( = ) and if ya do the twist together technique to join the resistors and wires they can fail to make good connection and the vats will read as no resistor present.
What I ended up doing was grab the section that runs down column from key, got as much of that as I could pull out, and then soldered each combination to the wire each time I tested it.Then you can just unplug yours under the dash/column and plug in the tester for good connection each time.Seems like alot of work but it worled for me.Good luck.& remember as much of a pain in the butt as it is it's a learning experiance to be savored when you finally fix it.(LOL Yea I buy that )