On the design of the boost control system I have to agree with ElanLover - it does the job perfectly well under the conditions it specified to run at. I suspect the squish in the exhaust is there to guarantee adherence to rules regarding the minimum distance of the exhaust from structural parts of the car rather than as a feature to avoid creep. I strongly suspect an un-squished 2" system would not suffer from creep as simply fitting a gasket with a 2" apeture at one of the unions of a bigger bore exhaust is a known fix for creepyness. Another point of detail is that the BCFV isn't there to limit boost but to increase it i.e high duty -> high boost, zero duty -> passive boost control at the wastegate actuator activation pressure (should be 0.4 to 0.5bar max)
As far as solving creep goes personally I couldn't be bothered with the whole remove turbo and port wastegate thing. I'd just fit a restriction (thus doing the exact bodge you criticised before
) Why not? The primary function of a big exhaust on a turbo engine is to let the turbo spin faster and produce more boost. However, the stock exhaust allows the turbo to reach boosts at the limit of the fueling system's capability anyway, so there's really not much to be gained. A little extra boost at low revs maybe but not really a huge deal. Most of the noticable effect on power is because of the creep! A slight restriction 2.25" is still going to offer less resistance than the stock system. I blame the big exhaust fad on all those sites that say an exhaust bore of x is good for a power of y bhp - you need a complete engine setup able to get that power not just an exhaust.
I still run 2" exhausts on both my cars. The Peco appeals a bit because of it reputation for making a good noise but then apparently some of them screech at high rpm and that doesn't appeal.
I think I'm going to be the unpopular one after that - I'm going to get my title changed to 'wet blanket' any day now.
PS when Geoff was talking about the £300 above he was talking about the price of the superchip - not my services! I reckon it could be read either way...
That's the most plausible explanation I've heard to explain the carefully squared exhaust section / squish. Having read Mark Hughes' book, I couldn't understand how Lotus had expended so much effort in development and proving only to be caught out at the last minute by boost creep; even less that the solution was to send the exhausts round to the local blacksmith for a few taps with a sledgehammer.
As for timing the creep, it all seems just a bit fraught with danger for me to get any accurate timing - watching boost guage with car madly accelerating, operating stopwatch, while trying to keep an eye on the road..... "Sub-optimal", at best! 
I think I'll wait until I get ElanScan working nicely, then let the computer do all that for me! 
I've just been having a look at my old squished section and it is D shaped which approximates to a semicircle on top of a rectangular section. It is a lot wider than the standard 2" diameter and I estimate its csa is about 95% of the 2" pipe. Interestingly, just back from the cat is a narrowing which is ~1¾" diameter or 75% of the csa.
