Sometimes the least expensive solution is to have someone who knows what they are doing look at your car.

Our '90 744 turbo had some starting problems that I could not find. A proper diagnosis revealed an altered throttle position sensor as a result of a hole in one of the turbo ducts. The car thought it was running at 5000 rpm when it was trying to start. I didn't want to spring for the hose, but the repair has lasted 5 years so far. I later found that the car's thermostat was doctored to stay open because the electric fan was dead.

Unless you purchased the car new and maintained it properly, your car is like a box of chocolates - you never know what you might find.

How did you go through 8 cars in 10 years? That sort of sounds like the car ad that goes - "If they weren't so good, why would I have owned so many of them?"
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96 855R, 95 855,854, 90 744 Ti - 310,000 miles driven