Could it be his fuel pump relay? My buddies 90 300E relay was giving him trouble because it would overheat and shut off, but we never knew when. Only thing was his did get sluggish and all that..

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76 MG Midget
78 Datsun 280Z
86 Peugeot 505
01 Subaru Outback

“Owning a car is like owning a dog. Every now and then, it craps on the carpet — but it’s still your dog.” - Jeremy Clarkson