Lightforces are probably running at 100 watts each. The stock TJ fog lights are probably running at 55 watts each.
55 watts divided by 12 volts = 4.5 amps per bulb = 9 amps for the set
100 watts divided by 12 volts = 8.3 amps per bulb = 17 amps for the set
Check your fuse block to see what size of fuse is being used for the fog lights. If it's a 20 amp fuse, knock yourself out. If it's a 15 amp fuse, you will blow it.
You will honestly get better performance out of those lightforces if you run a completely new homebuilt wiring harness with relatively heavy wire, and just trigger a relay off of the fog light system...that will also prevent any problems you might have with drawing more current thatn the stock wiring was designed for. The relay will probably run you $10, and the wire is probably another $10. Mount an inline 20A fuse close to the positive terminal of the battery, solder and heat-shrink your connections, and Bob's your uncle.