EP2 temporarily runs slow

[JDR33]

I bought an ep2 off a guy not long ago and i was aware of this temporary slowness issue before i bought it. He replaced the 02 sensor which left the EML active which is one issue i need sorting out but basically on random occasions when slowing down or driving slow i go to push on the accelerator to gain speed but it struggles badly so i change up a gear which slightly improves for a very small amount of time but then goes back to being slow. I would say it happens for around 30 seconds before going back to normal again.

It feels as if like a maf sensor has gone faulty except not on a constant basis or your about to run out of fuel though doesnt cut out.
Can anyone help out at all on this? Thanks.