If you want the best pre-cleaner, get one with an exhaust ejector.    Donaldson is my first choice.   http://www.donaldson.com/en/engine/support/datalibrary/074396.pdf        The Turbo II will help, but watch out for the pre-cleaners that dump the dirt right above the intake.  They will suck much of the pre-cleaned dirt right back into the air cleaner if the vehicle is not moving fast enough to blow it away.  That is a stupid application for any slow moving vehicle. The original Turbo pre-cleaner did that, and I am disappointed that Donaldson recently introduced a few pre-cleaners like that.

Donaldson has dealers almost everywhere.

The Donaldson web site from above shows a check valve for the ejector hose that feeds into the exhaust to prevent that from happening.

I know a guy that had to overhaul his combine engine last year because the exhaust burned a hole in his air filter.    Dusted that engine pretty good

You have to do it right.  The check valve is required.  I have two spreaders with exhaust ejector pre-cleaners and I eventually either clean or replace the air filters when I can no longer stand not doing it.  The restriction indicators never come close to the service point.  I realize that a spreader is not usually in the trash and dirt like a combine, but the difference in cleaning time is huge.  I do buy the expensive Donaldson service by restriction air cleaner elements, not the standard ones that you can get at the parts store.