In short.....
Why do you want it? - you will only really benefit from anti lag for racing or 1/4 miles/launching etc, tight circuits where the cars needs to be kept on boost. If your not doing any racing and its just for show.... then its a bit of waste. There are exceptions to this rule, aftermarket ECUs often have these sort of things built in anyway.
Do you have lots of cash? - Antilag kills turbos fairly quickly. If you'd like to rebuild your turbo every once in a while then knock yourself out.
I've done some work on my mates evo 9 which runs about 400bhp. The standard engine has an ALS built in, but its not activated. There is an accumulator pump that gets boost from just before the throttle and has piping to vent it into the exhaust manifold. This might have been to comply with GroupN (or is it Group A) rallying - i.e built it into the standard car but don't activate it.
The evo boys have found out how to activate it now
