...and was trying to use small firecrackers to ignite the powder (why not a match?)...
Where are you reading this? Every major news source I am looking at is still reporting that he used a syringe to try to start the reaction. The only reference I've read anywhere about firecrackers are passengers references to the noise the thing made, as in it sounded like firecrackers.
MSNBC
"The device consisted of a six-inch packet of powder and a syringe containing a liquid, which were sewn into the suspect's underwear, according to media reports."
BBC
"Mr Abdulmutallab allegedly tried to detonate a device using a syringe, but it failed to go off."
CNN (Reuters)
"A preliminary FBI analysis found that the device contained PETN, also known as Pentaerythritol Tetranitrate, a highly explosive chemical compound. In addition, FBI agents recovered what appear to be the remnants of a syringe from the vicinity of Abdulmutallab's seat, believed to have been part of the device."
Etc.