Got myself a run around car, it's an 80 something Magna. One of the old ones with the Astron 2 2.6L engine

Now, at low rpm (under 3000) it chugs, kinda like bunny hops but not quite. Gets worse the more load there is on it (ie, higher gear)

Wondering what this could be?

I was thinking leads and/or plugs?

Also it is quite slow and kinda has that WRX sound from the muffler, making me think 1 cylinder might not be firing properly? It isn't rough though through the revrange