Hi Sean
The system will not self regen with those pressures, remove pipe from exhaust pressure sensor, substitute your own pressure from Mityvac etc and set about 60mb, request regen and drive moderately for 15-20 mins on d/carriageway and watch exhaust temps climb to 600c.
OR, phone John Hoole at Wunoff exhausts in Bradford 01274 619070, he has an industrial oven for cleaning and does a great job.
Ed Kaps