Engine was shutting down when cold for first mile when brake was applied. I found vacum leak in brake boster. I had Brake Booster replaced for $435.00. Now it will shut down every time I stop car for the first mile or so untill the car warms up. After that no problems. Replaced spark plugs. Did not help. No error codes. Runs rich. I was told to adjust valves for another $300.00 but no guarantee. What do you think?