ECU setup for pulling tach signal

[itjstagame]

Ok, I've read quite a bit and stagnated quite a while since soldering up my ECU. I'm ready to just plunge in and see what I get but my main remaining hurdle is making sure my ECU is correct.

I'm squirting an Audi 10vt, that's a 5cyl turbo, an MC1 to be exact. Anyway I read lots of things suggesting it's a 60-2, this makes sense to be because I'd think it need to be a multiple of 5. Anyway I was in contact with someone that suggested just pulling the tach input from the stock ECU.

My question is how can I tell what type of signal this is? Do I have hall, vr or do I set up for negative on the coil? While I'm here, what does negative on the coil change really? I understand that hall is square wave and vr is curved but negative on the coil would act as a square wave, wouldn't it?

After I know my ECU is setup right I can feel better about hooking things up to match.

Thanks.