backfire and vibration

1993 Mustang LX Hatchback 5.0, Black paint, black interior with white pony wheels. Black Magic electric fan, Griffin 2-row alum radiator,Under drive pulleys,air cond elemination pulley,BBK castor camber plates,crane coil, msd,1 1/2" unequal length shorty headers, off-road X-pipe,flowmaster 2 chamber after cats,urethane tranny mount and cross member bushings,manual adjust clutch quadrant, steel throwout bearing retainer,driveshaft loop,sub-frame connectors, alum driveshaft,pro 5.0 shifter,190 lph fuel pump, cobra intake, C & L 76 mm mas and ford motorsport 65mm throttle body, Mega bite jr lower rear control arms,rear-end girdle,3.55 gears,cross drilled front rotors and stainless steel brake lines,king cobra clutch,adjustable fuel pressure regulator,battle boxes since I busted loose the torque boxes.82 mustang heads ported with 3 angle valve job. I am sure I am missing something.

When I start the car for say the first time of the day and start driving it sounds as if it is back firing up in the engine compartment and there feels like some sort of vibration in the trans area at diff rpms most noticable around 2,000 in 5th gear. Any idea's guy's?
:feedback: :disappoin