Searchy

Hey this is my first post and unfortuneately its an ask for help one, i have a 2000 awd turbo MY99 uk spec, ive had it a few years and wanted to get adventurous with it, so ive installed general bits n bobs and on the weekend i installed the HKS SSQV blow off valve, now i've got a de-cat exhaust system and it does its usual popping on low revs which i love but now it mis-fire's too, any thing to be worried about?

Cheers in advance for your help