Akroblade: The only thing that a tuner could adjust on an R without aftermarket ecu or fuel/ignition computers is the base timing. I wouldn't bother with it if you have already had it set for 1 bar. Unless you want to raise the boost.
As for plugs, I use Denso's also. I got mine from
www.sparkplugs.co.uk Email them and say you want a grade cooler than standard, I think IK22's, they will do the rest. They were about £45 all in. All the other tuners plugs i.e. Blitz, Hks etc.. are just re-badged and over priced NGK or Denso plugs
Pete-R: Engine Advantages no is as follows: 01375 502522. I got there details from Xtreme Scoobies near Boreham. Thought I would give them a try. Strange this is, Essex turbo's are in the lock up next to them. I have the car booked in for 13/10 so, will let you know how I get on.
Cheers
Paul