Hesitation

[ajas123]

Hi there,
 
  I would appreciate some pointers please! My FD (unmodded) developed a hesitation last year around the transition between the primary and secondary turbos. I though it was to do with the vac/pressure system, and replaced several solenoids and lines. But, the problem is just getting worse. It now hesitates through out the rev range with the slightest press of the accelerator. I am now thinking that it is something else! Any thoughts on what will cause this? The boost gauge reads steady pressure even while it is hesitating. Is it fueling? Ignition? Any help would be appreciated!
  Thanks!

[nikp]

When was it last serviced? My thoughts would be an ignition issue, and therefore would ask when A. Spark plugs were changed and B. HT Leads. Both these are serviceable items and needs to be changed during the relevant service.