surge problem on 1.8T?

[Dave-B5]

alrite guys my dads brought a 1.8T satt after drivin mine b4 i sold it, its been a dream since he got it.
but now its surging (ie;a little brust of speed) when u hold it at a constant speed. and its at any speed, had it vag com'd at my mate (apd) and no fault codes came up. we've also checked for cracked boost pipes with no luck. im doin a service 2mora but im not sure it'll help, anyone got any ideas?

any help would br great guys?

dave