The problem with a "cheap Porsche" is that many who can afford to buy them, cannot afford to own them. This is why so many that break get sold at pennies on the dollar.
The Cayenne engine is the only watercooled Porsche engine that impresses me from an "over built" standpoint. We are enjoying building the engines and they are super, super heavy duty internally. There are no internal engine issues other than cylinder failures on the S models; but those seem to only occur in cold climates as the turbo version has factory Nikisil bores. (thats the reason why we started the Cayenne engine program and mostly just for the Canadian contingent)
I have a Turbo Cayenne and my Wife drives it daily, we both love it. A little tuning and some mods go a long way quick with these beasts. The turbo just rolled 100K miles and is still going strong, even with a whole lot of experimental oils being fed through it.
Here are some pics of a big bore, ported, high compression "S" engine known as the Raby 5.1. Its a true beast, gets 24 MPG and has neck breaking throttle response.
More build pics here:
https://www.facebook.com/media/set/?set=a.641338479227284.1073741840.184464434914693&type=3