If I was to change the intake manifold on a 92 civic dx to a high flow intake manifold would i have to make any other changes or could i just put it on?

depending on how much more flow u may need a bigger fuel system.

yea depends on the mani some will bolt right up others might need some work.
if you just snag a y8 mani little work its a nice set up i ran one on my a6 was great. but as far as other mods you dont need to do any but never hurts