this could be a vacuum leak after the MAF (mass air flow) sensor thats mounted on the air intake pipe
any air pulled in here post meter isn't 'seen' by the ECU and so not compensated for and results in the engine running roughly and hunting as you describe
the best way to locate an air leak is to have the engine running and then spray lighter gas around each possible joint / rubber hose etc post MAF
if there's a leak then the engine will pull the gas in and rev up
now its not as dangerous as it might sound as you need a naked flame or spark to ignite the gas and I've used this method for many years without incident
usually this sort of thing is a cracked or perished rubber vacuum hose, so can be repaired very cheaply
do you still need help?
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