idle drop after putting downpipe and catback
 

I just put a downpipe and a catback on my 93 FD. Is it normal for the idle to drop a little bit?

you have less back pressure now so yeah

Less backpressure at idle? If his DP was clogged up that bad, his engine probably didn't even run past 4000 rpm. If anything, more flow at that point would result in the idle being higher.

You most likely disturbed something else during the exhaust installation to result in the lower idle. Are you sure the O2 sensor is plugged in and working properly?