thought i'd update what's gone on with my car...
the additives were at best a temporary fix about a month after using them my 'bamma was back to square one and getting worse, usual symptoms - unable to pull more than about 65 uphill in any gear, warp field collapse (limp mode) if i drove it enthusiastically, lumpy acceleration in low gears and none at all in high gears - absolute max speed was 90mph downhill (on a private road m'lud). finally got together the money for fixing it if it came to the worst, so took it along to jabbasport in peat-bog-horror and asked them to fix it.
first
problem - knackered MAF so that got replaced.
still not going well so off came the turbo and lo and behold it's seized solid.
unfotunately my bamma has a weird turbo more commonly found on a sharan aparently ??? so it took a day to sent the one that brian had ordered back to wherever and get the correct one.
unfortuantely whipping off the turbo had revealed that my exhaust was composed mainly of rust and road grime so a new one of them had to be sourced and fitted.
at this point my credit card cried 'enough' but fortunately this seems to have done the trick. acceleration is now smooth, i have torque again and it;s still pulling at 100 (on a private road again m'lud). it doesn;t feel quite as frisky at the top end as i remember but then it's been a while and i'm guessing a lot of soot and crap has passed through (and stuck in) the intake system since then.
so in the spring it's going to be back to jabba for a service, intake cleaning, egr disable and possibly a session on the rolling road with a laptop if the insurance doesn't hit me too hard.
big thanks to brian and the guys at jabbasport for sorting me out.