So I think I'm going to buy a Eheim 2217 filter. Its for up to 160 gallons.
As of right now I have a 55g and a 75g.
My question is,
Is there anyway that I can run this filter with both of my tanks, using a hose splitter making 2 intake lines & 2 exhaust lines? Instead of just 1 of each?

idk for sure. but i would say no.
if u think about it, what if 1 hose is spiting more water than the hose is sucking out. it will over fill. or one tank would over fill.

Yea, I see your point.
But do you think if I used valves to control the amount of in take and exhaust it would work?

no a cannister filter is not designed to work in the way you are suggesting, the only way you could make 1 cannister work with 2 tanks is a waterfall/overflow effect in which the cannister would pick up from a lwer tank and return it into the upper in which the upper tank would drain into the lower like teh plant tank in petco.

Ok thanks for the help guys!

I've decided I'm jus gonna use it on my 75 gallon.
It will probably work out good bc I have 2 full grown O's in it.
And the extra 84 gallons of filtration will be needed bc they're very messy fish haha