LLL,
Cheapest would probably be a manual bleed valve type arrangement which you could probably sort out for about £10 or so ranging up to the Apex'i AVC-R and Blitz SBC-iD which are around £500-600 I think and then onwards to a fully programmable boost control setup likt the one that is part of a Gems ECU which is around £1500 fitted and programmed (but this is a full ECU so does a lot lot lot lot more than just boost control).
In between you can get cheaper versions of the Blitz and also the HKS EVC.
It depends on what you want. If you're after a boost controller that you will just pick a level, leave it at that, not worry too much about changes in boost level due to atmospheric effects (i.e. cold weather, changes in humidity etc...) then the easiest would probably be a manual bleed valve.
If you want an all singing and dancing electronic in-car adjustable boost controller where you can play around with boost vs revs (Apex'i only) and set overboost limits etc etc then you'd be better off going for the Apex'i, Blitz or HKS (depending upon which features you are after)
If you are going to be doing a lot of further modification to your car like different turbos, cams, internals etc etc then you'd be better off going straight for a fully programmable ECU that has a good boost controller as part of the overall package like the Gems.
Hope this helps
Andy
