There is a secondary fuel module(don't know what it is called) mounted on a bracket on the top radiator support that may have gone/going bad. That happened to me, but within a couple of days, the car would not fire up at all. What year SHO? If you are getting spark, that is what I would look at.
John
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John
1992 Mustang LX 5.0-Powerdyne BD-11A, 3.73's, FRPP clutch, chrome Ponies, Mac headers, Aeromotive regulator, MSD 6A, MSD BTM, FRPP 42# injectors, Pro-Flow Air Optimizer, Trick Flow Track Heat intake, Edelbrock 75MM TB, AFM Power Pipe