I've got a '91 RS 305ci TBI and i'm wondering if a spacer would be a good investment or simply a waste of time and money?

(i also would like advice on a good cam to put in)

IMO.. the best investment would be a VAFPR and RBob's EBL, learn how to tune it will be better then any spacer.

Its worth it.. But then again its not. If you are going to throw in a TB spacer and thats it, you wont notice very much. What you Need to do if you havent already is the Ultimate TBI Mods's That are at the top of the TBI Forum/Section. and throw in that spacer. That will give you some results.
Howevere that EBL thing is new to me, Guess I gotta check that out!

Id avoid the spacer mainly because of the TV cable geometry. If thats off, it can ruin the transmission.

I Made my own out of Heat Resistant Plastic. My Father got some from the Mill, we made our own slides for the snowmobiles, And they havent worn very much in the psat 3 years. Anyway I Have a 1/2" Spacer and it didnt Change a thing. If you had anything Bigger than 3/4" inch I think You would Change the Setting of the TV.