I'm no expert, but if the exhaust is restricting the flow out (and therefore the charge in the cylinders) and that restriction is removed the engine will breath easier allowing it to accelerate to higher revs faster and produce more boost as a result of the higher revs.

Same boost at any particular RPM but if you're talking about 0-60 or 1/4mi then it will produce more boost due to getting the revs up quicker.

Although I agree it's probably a placebo as much as anything wink

'93 16V Mondeo saloon
Full factory RS setup lowered on 17s
K+N 57i, splitfire leads, chipped, full aluminised twin-exit exhaust
Sounds by Alpine, Infinity, Vibe, JBL
First Mondeo with indiglo gauges