I have a 1988 ford f350, when I start it up it idles very rough and when you stop at a red light it acts like its going to die. When driving it normal it runs great but once using it for towing its seems like your pulling with a 6 cylinder not a big block 460. Not sure if I got a vacuum issue or the EFI. The truck only has 48,000 miles, 2wd single cab dually 5speed. Thanks for any help.