I don't know, it may be my non-technical expertise, but I would highly suggest you take the 'stang in for an exorcism. Look in the yellow pages...
If that fails, fuel filter.
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89 LX 5.0 Notchback, near showroom condition, Flowmasters (my dream since 16)
98 Grand Cherokee 5.9 (Very rare and hence a driveway princess), 90 VW Jetta Diesel (200K, 45 MPG and all hers), 87 Cutlass (mine) 84 Cutlass (170K of faithful service)87 Bayliner 2250 Cuddy