If there is a flaw that bad in the 91 Celica's then this is what I would be doing.. First change the alternator and the battery..
**(Never ever start up an engine with a new alternator without first having your battery checked and charged at a parts store because it will destroy your new alternator if your battery is either bad or undercharged)**
Then after that do what this guy did..
http://www.automotiveforums.com/vbul...d.php?t=209543
I did that to my 88 Chevy Beretta and it did wonders