323 98 losing accelleration
 

hi my 323 1998 is losing acceleration feels like a clog in filters the revs were going up & down when idiling and last week it died with batt light coming on, was told i needed a new alternator which i got and now the revs are staying at about 800 when idiling,however it has not stopped the accelleration loss, i have replaced the plugs and filters anyone any ideas,is it a job i could do myself, i hope so as ive just replaced the alternator and one of thr rear shockers which wasnt cheap, thank you:eek: