I've been using the Amsoil system on my 2nd Gen for 7 years now, have the unit with 2 filters. I mounted it under the front bumper , so it's simple to change filters. Been using an oil analyst for years, and based oil changes on the results, which has been around 25,000 miles usually. ( filter changes in between oil changes) With well over 300,000 miles on it now, the entire system works well for me.
good luck