Hiya Martin,
( and thanks for the 'summoning' Phil and Andy

)
Yes, I loved M.Qs in a 335 Copy, found an Alnico II magneted Stormy Monday set left the bass strings a bit soft/ quiet in Basswood ply and mahogany neck ( so the good news is that your Maple model will probably need less 'help' ).
AIV magneted Stormies were a great balance, but the M.Qs took control, whilst also giving me all the degrees of sweetness in-between.
I would however ( in your case - or mine with Mules in a genuine Gibson ) heed Tim's advice - and add my voice to the chorus that say " drop the neck pickup lower, till it sounds right"... e.t.c.
I have Mules in a Les Paul Standard, so know that the neck pickup is not intrinsically boomy / bassy -
but probably would be more so if set equal to the bridge p/u in a 335. There is the 'softening' effect of the cavity / hollow body to factor in.
Manahattans are too elegant and 'retro' for general use ( but a match made in Heaven for smoooooth or 1950s Jazz sounds) I left some 'Komedy Klips' of the Manhattans in the 'Players' section recently - to "eliminate them from your enquiries",.
So, keep what you've got, and have a good twiddle of relative bridge / neck pickup heights -
but make sure your Tone and volume pots are really 500K ohms ! as this could really be working against you if they are not !
( I had an 1976 Gibson S.G that came with with 300K pots !).
Beyond that, M.Qs are 'good to go' - and give a unique twist to that quintessential 335 tone. I could only get authentic Larry Carlton tones / tighter bass / fat sweet treble - with M.Qs in my 335 copy. :)
Do please , please check your pots though, It sounds like you may have a bad case of '300K-itis' .