Hi All, im new to the site looks cool..and hope someone can shed some light for me?!

A few weeks back i had my 2.5 elite serviced and the mechanic noticed the rocker gaskets needed replacing as there was oil
in the plug wells, i had this changed as it was affecting the drive, as in choking up etc..i thought as it was covering the spark plugs it must be this...but its still playing up after the work. nothing appears on the scan not 1 fault code, im sure its not a missfire, it will behave from cold, i drove it 30 miles on the A2 and back to my house and it seemed fine as soon as i slowed to turn right i touched the throttle and it choked up and stalled, it started fine then again when i slowed the revs dropped right off very erratic at low revs...also i revved the car up to around 3000 rpm and took my foot off the gas and it dropped off and stalled..funny how this only happening after the car is warm etc
Any thoughts would be helpful
Had new plugs,air filter,crank sensor, o2 sensor, coil pack, and leads around 3 months ago