Hesitation bug, and bad idle

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I am havin a very weird issue. I get a bad hesitation almost like the ignition cuts out, if I am on the gas usally in a higher gear 4th 5th and I let completely off and then hit it again quickly. if I apply the throttle slowly it will not cut out. it has happend before but got worse when I added a C&L mass air and 30lb injectors, the car also does not idle since I added the mass air and injectors. when it does idle it has that pulsating prob that other stangs have at idle where it revs up and down is that the map sensor? If anyone as any ideas please let me know thanks