So i brought my car to a performance shop because it was running like **** they said it was a bad COP re did the cop did an inspection long story short 2500$ later im still in the same boat car idles like **** feels like it has a miss fire. I cleaned the maf and it idled good for a day. Also if i remove the air filter from the maf it runs way better but still missing. Every time i pull the plugs they are all black smrll raw fule when under load. Looking for a decent price maf

 

Looks like you're in North America, however when it comes to MAFs buy Genuine OEM, don't cheap out on it. With it being a JDM car is it mapped to local fuel?

What air filter are you using?

Other things to check, idle air control valve and coil packs. Might be other things to check but thats all I can think of at the moment.

 

I changed the maf with oem didnt help

 

Another way to check the MAF, have the car running and pull the MAF out while it is still plugged in. If the car stalls MAF is ok. If it doesn't MAF is bad.

Then have a look at the other bits, IAC valve might just need a clean.

What did you spend the $2.5k on.