Aftermarket gauges Speedo etc.

I purchased a set of after market gauges through one of the mail order houses. I guess they have to use generic instructions but... are there any that refer to the VW system?

I put in a gas gauge, speedo and oil pressure and following the instructions with them wired etc them in to my car. Then I find out I can not do this as the VW system is not set up that way and I was not getting a charge to my battery due to the idiot light ( OK no jokes please!!) was not wired per vw specs.

Sure liked the brighter gauge lights though., anyway, in frustration I just went back to the stock parts.

Any advise??

Thanks, Mike West