When I had my timing done my mechanic pointed out that my car was misfiring, so today I changed my plugs to see if that would correct the issue. None of the plugs seemed to be fouled put, but I changed them anyway. I used ngk iridium one step colder plugs. After the change, my car was misfiring much worse, and ignition timing was all over the place (it was around 13 before). Any ideas? I'm going to check the connections to all the coil packs and clean them but I'm not that knowledgeable with issues like this.
2002 wrx
Catless Uppipe/down pipe
Manual boost controller 15 psi
Borla hush exhaust
Open source mild tune (a little rich but not enough to cause problems)