i have a 98 eclipse rs when putting it to P, R, or D i'd get a clicking sound dont know what it is..also when slowing down to a red ligth or whatever car will jerk or slip then hit kinda hard for some reason.. what do u guys think it is ..pleae help

i only put cat back exhuast system with air intake system ..tryin to build it up but trying to find out what this problem is first.