Does the cannon of the A-10 deliver more thrust than the engines do?
The A-10 uses a GAU-8/A. According to Wikipedia:


  The average recoil force of the GAU-8/A is 10,000 pounds-force (45
  kN), which is slightly more than the output of one of the A-10's two
  TF34 engines (9,065 lbf / 40.3 kN each). While this recoil force is
  significant, in practice a cannon fire burst only slows the aircraft a
  few miles per hour in level flight


Your statement is only partially true: two engines have more, but one engine has about 10% less thrust than the recoil force of the cannon.

The recoil force of MiG-27's GSh-6-30 was even larger: 60 kN.

As pointed out in a comment by @tj1000 the recoil of the GAU-8/A wasn't such a problem as the smoke from its shell propellant. If you're looking for the video mentioned in the comment (test pilot ejection due to engines out after firing ammunition with a new flash suppressor) this is the link (12:08-13:59).