There is a lag when using a FMU between vac and boost. If you are cruising in first and romp the throttle, there is a delay, then you get boost. I didn't care too much for it, so I went with 42#'s and ditched the FMU. I sometimes have hard starting problems like you described, but it is only when the car is runing, then I shut it off and try to start it again. But, while the car is running the power is smooth, not spikey.
John
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