Originally Posted by
RafalGTZ00
Sounds to me as though your fuel sensor isn't keeping up with the Turbo at higher cruise speeds. It's running lean because the turbo is pumping in extra air (like it always should) but the car's not expecting to need the power. When you try to accelerate fresh off that cruise point, the car actually approaches a stall as the air:fuel ratio goes even weaker. This wouldn't be a problem under a sustained acceleration because the injection system is expecting to dump in tons of gas. Dropping out to neutral dramatically decreases the amount of air being crammed into your cylinders by the turbo as a result of less exhaust from the idling engine, improving your fuel:air mix once again, until the car settles back into a sedate cruise mode.