You'll get a lot of naysayers in this thread I'm sure, so throw on your flame retardant suit
As far as flushes, the only thing I've ever used and can vouch for is seafoam. 1.5 fl. oz. of seafoam per quart of oil crankcase capacity. Dump it into a cold engine (doesn't sound smart to dump a room temperature liquid into a 100+ degrees crankcase, right?) and run the vehicle as normal for a couple days; depending on how brave your are.
Some people say there's a risk riding around with the Seafoam in your crankcase - BUT, right on the bottle and their website it says Seafoam can be used as a POST-oil change treatment (dump it into fresh oil directly after an oil change, and change the oil at 3,000 miles), or as a PRE-oil change treatment (dump it in before your next oil change, but monitor oil color; if the oil gets too dark [black] then change the oil, don't go more than 3k with the Seafoam in the crankcase).
You'd be following the PRE-oil change treatment. Sure, I wouldn't advise WOT runs at cold-start or anything of the sort
But other than that, I got compliements from the KIA tech who serviced my vehicle after a Seafoam treatment. No, I didn't tell him I used Seafoam; lol that's my secret. All he could say, "oh must be that Bulk Pennzoil we got here!" pfft...lol.