Air flow in 2x4 grow tent.

I have a 190 cfm fan throwing hot air out of the tent and just have the bottom vents open on the tent. I feel the air being sucked in. Can I just close them up and add ducting to bring in fresh air or the fan does not have enough power for that?

you can get cheap booster fans on Amazon that fit right in the slots on the tents and as long as the CFM rates good for your size of tent it should be fine.

get a 6 inch centrifugal and a speed control, I used that in 2x 4 cabs and it worked well.

Make sure your exhaust is pulling the tent walls in a little - if your tent leaks, it will leak to the inside & keep your smell under control.

I'm using a canfan 6in has a built in speed controller , its cooling 260w of led

Yes, you can close the square vents and then use duct from the small round holes to pull enough air through the tent. Not sure if your fan is large enough without more info, but you will know when you try.