Yup HJM its a 1983 Fender Esprit Standard - a chambered alder guitar with a maple top, later became the Robben Ford model. I bought it new as a teenager but gave up guitar for about 20 years, so it has sat in the loft.
The old stock schaller pups were dull and grunted = they totally nullified the effect of the chambering.
The mule and MQ (both A4), on the other hand, bring out the chambering in a glorious way - the guitar now has an added acoustic dimension, almost an ES335 sound.
I've been playing Peter Green type stuff this morning and the MQ nails it nicely. The mule on the other hand has a smooth Gary Moore blues tone (I suppose that's also a Peter Green sound as its the same guitar) and whats more the MQ has no discernable noise.
Middle tone is - wow! - it has that quacky sound of two humbuckers but with an added, almost strat bridge-middle, out of phasy tone. Slight volume drop but just pure.
All in all it has turned a guitar that sat in my cupboard for years into a tone machine!