Low power

[kjc1969]

Hi i have a 2015 2.2 transit custom. Always been low on power since i bought it, so i had it remapped. Didnt make a massive amount of difference to the power. If when  im driving i "pump" the accelerator it feels like it wants to pull. But foot flat to the floor and its as flat as a flat thing! Recently its developed a misfire/lumpy idle when i lift my foot off the clutch and the revs raise, but seems to clear at around 1500rpm. I noticed the other day as i drove past a building with my window down that it made a rattling sound under hard acceleration. once on  light throttle the sound is inaudible.Do you think it sounds like injectors?

All filters have been replaced recently.

 

Thanks for any suggestions