Couldn't agree more with Steve.
I tinker with my car because I enjoy it and want to learn, I make mistakes which cost money and time a professional couldn't afford.
When the job looks too difficult or I really need the car next day, guess what, it goes straight down to my local independant. If I don't feed him with work occasionally, he might not be there when I REALLY need him !
Don't fight the car, enjoy it. Sure I hate it when it beats me and I have to call in the pro's, but then I move onto the next easier job and feel good again.
Saying all that, Cap'n I feel for you, it sucks when the problem resists all attempts to fix it.
Best of luck.
1989 W124 300E
1991 R129 500SL