Bel are the apexi Distributor's and i've seen and experienced their work first hand.
The thing I like is they actually do a road tune. Compared to a Dyno. So you can tell them how you want the car to feel say you wanted lots of bottom end for hill climbs/Touges etc. And they never push the car 100%.
We had the WRX done at RUF it was making big power for a stock engine 185kw@all four. It ran real rich bottom end back firing alot on the strets but had a top end rush.
Got Bel to make the car more drivable and they did a really good job. Bottom end was great it had sharper throttle response and boost came on earlier. Didn't feel as strong as the max tune. But alot better to drive.