I bought the Q industries MV-50 in '07.
The QC is far from impressive, but a little spit and polish goes a long way.
First, the little air filter, most of the inlet holes were obscured with flashing left over from the mold. Highly restrictive. As such i did not employ the air filter at first, and it wound up sucking in a bunch of dust sand and debris, which compromised the piston skirt's efficacy and the reed valves inside.
I found the cylinder head bolts finger tight at best, and the cylinder would only touch the finned heatsink in 4 small areas around the perimeter, if it were machined perfectly. But the cylinder outer diameter is loose within the heatsink's inner diameter and as such only one of the 4 mating surfaces can actually be in contact with the finned heat sink, and there would be very little actual contact between cylinder and heatsink for direct thermal transfer.
I also despised the thread on hose it came with and the metric fittings did not allow for simple standard 1/4 npt air hoses to be used.
There was NO strain relief where the 14awg wires entered the tail cap and attached to the standard 30 amp bosch style cheapo chinese relay. The connections within were crimp nuts, the spade connectors onto the relay were extremely poorly crimped. The inline fuse holder would get ridiculously hot after a minute or 2
I used a razor to remove all the flashing to remove restriction on the air filter housing.
I retapped the head for 1/4 NPT threads used a better more flexible longer coiled hose and a locking tire chuck that I made passive so it could npt allow pressure to build in the hose when not connected to a schrader valve.
I cleaned the reed valve and flexible piston skirt and lubed it with syl-glyde.
I filled the gap between cylinder head and heatsink with high temp grease to better conduct heat from cylinder. and retorqued the head bolts evenly.
I redid all the wiring to switch and relay and added an 80mm computer fan to blow over the heatsink.
Needless to say, it works much better than it did out of the box.
Is all this effort worth it over buying a higher quality more expensive Viair to begin with?
Perhaps, perhaps not.
It draws 16 to 18 amps depending on the voltage it is being fed and the pressure of the tire/airbag.
It is by far the best 12v inflator I have personally used. All previous ones with a ciggy plug were very short lived, and became noisy tire deflating noise makers instead.
While i have a pancake style AC compressor, If i am only doing small PSI changes the MV-50 is faster to use compared to setting up the pancake compresor filling its tank, transporting it to the tires.......