The BMW 535i (3.5-litre six-cylinder model) is a good package - it wouldn't be a BMW if it wasn't. it'll do everything you ask it to do, with a little 'spice' mixed in. Go a little harder, and you'll encounter two large flat spots where the power just falls flat, then picks up again (around 3000 and 5500rpm). There's also a slight lag between gearchanges and an idle that isn't as smooth as it should be.
Immediately noticeable was the improvement idle - now a steady 800rpm (not as rough or with the fluctuations of before). Hard stabs on the accelerator also indicated the slight pinging was gone, while full-blooded runs provided an extra 500rpm to play with (fully useable too).
A seamless power delivery to the old redline and beyond means the flat spots around 3000 and 5000rpm are gone. The engine note has improved, mirroring the good gains in acceleration. Fuel economy is about the same, though emissions run a little richer (still safely within EPA limits).
Powerchip says the performance gain is attributable to the 16kW it extracted with the chip, which raises power to 171kW/229bhp - an excellent figure for an engine of this size.
On the track, the 5-series cut a full second off most of the times recorded using the standard chip, with some runs up to two seconds quicker. Particularly noticeable was the drop in the 0-100 figure (2.5 seconds).
BMW 535i (E34 - auto)