Misfire when warmed up !!

[Bluejuice70]

Hi all.

Need a bit of help guys, just got my 450 back on the road after changing the head gaskets, removing the pre cats and also tidying up the engine bay and fitting a Tornado chip.

The car is going great and sounding fantastic with the pre cats removed but when the car is warmed up and driving slow or in traffic it misfires and splutters, a quick press of the throttle and it goes away, any idea's ????

Cheers

[pacman1]

Not a techie, but is that not fuel evapouration? I could be talking balls though.