Won't stop backfiring when i move the car and changing gears

Check the secondary air system, could be a bad diverter valve or you lost the vacuum supply. You may need to pull the codes but you will need an scanner that can do old ford OBD 1 system.

There could be many reasons why this is happening. Timing belt could have jumped one tooth. take cover off and check timing marks at T.D.C. [need to set up timing mark on crank pulley ] The timing gears never go bad and the is no wear shoe. two rollers keep the belt in place. The converters on Capri's are known to brake apart and clock the exhaust pipe. also the 2 vacuum advance modules go bad. [changes the timing.] Does the turbo put out 12 pounds ? it is going to take the process of eliminations. My 92 Capri is now a MOON car. [do you know what that means?]