ipd will provide a conservative reprogrammed ecu, great company and reputation to back it up as well.

a few others to mention are bsr (customizable to ur liking), pes, and i'm sure there r some more...

moving boost up to about 13 or 14 psi (from stock 9.6 psi) is best way to do so. most suggest anything over 18 psi and u'r asking for trouble...connecting rods can fail to name one. a manual boost controller can temporarily get the boost up...but the ecu will soon recognize this (if u stay stock ecu) and cut off the extra boost.

Volvo has already heavily modified the block, pistons, valves, connecting rods.....

THIS is a relatively expensive modfication, but well worth it, IMO. You WILL go faster!

http://www.skipbarber.com/drivingschool/index.htm

Two required variables are missing. What kind of performance and how much money? IPD sells a performance package including ECU, exhaust, K&N (overrated), and top engine mount bushing for about $1600 I believe.

Of course there's always improving your HP/weight ratio but not everyone wants to gut their car. Go to turbobricks.com and read about intake restriction. Lots of valuable information there. For example, K&Ns and larger throttle bodies don't really add much except cost. By measuring the actual pressure drop across intake components they have shed light on where the real restrictions are. The stock intercooler being one I hadn't considered. Anyway, interesting stuff. BTW, their tests were performed on a 740t I beleive but the principles would apply to any engine.

The cheapest way to better performance is to keep your car in proper tune and confirm it meets spec by testing compression and leakdown. After that it's probably time to determine where you want to be and plan your mods accordingly.
--
Erwin in Memphis, '95 855t

It's hard to add power the "classic" way of freeing the intake and
exhaust with a turbo engine since it already has forced induction.
You can get some improvement with the exhaust but that is expensive
and increase is small. Adding more boost pressure is the way to
go on a turbo. But, most chippers recommend updating the exhaust
first (or at the same time) to keep exhaust temperatures in line
and to free up the exhaust since the chip is forcing in more air.
Try ipdusa.com or tme.com (IPD resells ZTME chips). $1500 should
get you close to 280 hp with bolt on parts.

As far as the K&N filter and "$ to hp ratio," that would be $40 to 0 HP.

the k&n makes your car breathe a little easier. added hp??? maybe.
dawes device boost controller - $+30 - you can increase boost and hold boost longer
or
you may opt for the real deal - chips. depending on what brand...ipd, rica,etc between $500-$900.
regards