Trouble is, when WUR's go bad, the result is high control pressure, which, while it makes for hard cold starts, also causes poor acceleration and poor cold running. Gas mileage might improve because the mixture is lean.

I would bet on a leaky cold start valve, a worn-out oxygen sensor, or maybe even a damaged o-ring in the fuel distributor plunger.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe