1990 accord lx

it sputters and spits and backfires.

i know to clean the egr valve but i sprayed cleaner on it pretty well and nothing happened really.. it seemed better at first and now its bad again.

my dads friend said that the intake manifold plenums are clogged and i need to take it to this guy who will drill them out clean them and tap them.

is that what i need to do? or do i need to go hardcore and like pressure wash my egr valve?
(my dad seems to think it gets stuck but i think its still just dirty)

thats a lot of stuff to read sorry.. thanks for any help