Ed Anderson wrote:

That old saying "..If it looks too good to be true ......"  is hard to fault.

Well, here's my attempt at collecting some real data.  An electric leaf blower...used.  The tip is constricted to three 3/4" holes that are advertised to produce 95MPH air.  I've measured it at closer to 80MPH, which I find more believeable.  The fan is 5" diameter, and has a removable shroud that exposes more of it so that it can be used as a leaf vacuum/mulcher.  It's rated at 12A/120V and has two setting.

I stuck a 3/8" tube down one hole, fed the pressurized air into a bottle of colored water, which was pushed up a 1/4" tube.  The tubes were held into the bottle cap with a squirt of hot glue.    I tested it full open, and then closed off each of the holes in succession.  The last measurement was a full static test.  I then removed the shroud and tested again.

                      Low setting(in H2O)             High setting(in H2O)
Full open           12.75                                          19
1 closed             14.25                                          20.75
2 closed             15.375                                        22.25
Full static          15.75                                          23


No shroud
Full open           8.5                                              12.75
1 closed             8.75                                            13.25
2 closed             9.25                                            13.5
Full static          9.25                                            13.75