A 'boxer' engine is a 'flat' one where the cylinders are horizontaly opposed, as on the VW Beetle, Porsche 911 and Ferrari 512 Boxer and Testarossa! A notable modern day 'boxer' engined car is the Subaru Impeza, although Subaru have also used 'boxer', or flat-4 engines since the early 1970's.
What's it called again (or how do you technically describe it) when decelerating and I drop it down a gear and (at around 1500rpm) the exhaust makes that absolutely wonderful bottomlessly deep rumbling?
Sorry to dig this up again but working for Subaru i feel i can shed some further light...
The turbo's warble noise is due mainly to the exhaust manifold pipe lengths being varied. According to service manager the WRX's/STi's are 10% less powerful than they could be due to this design.
When we have in a non turbo eg 'sport 2000' model with a big exhaust they sound alot like a conventional 4 cylinder. The non turbos cant afford to have the strange manifolds as they need all the power/torque they can get and only get driven by farmers wives/daughters.
Note the world rally cars dont sound as warbly as the road going turbos but this may be due to other reasons.
I genrally think the sound is boring now (especially now i have an Alfa GTV 3.0 V6) but the other day we had in a WR1 with straight through pipe that id love to get you all a sound recording of