car windscreen specialist

bros in ZTH... i nid some help......my car will jerk for 1 moment suddenly sometimes like wan to mati when normal drive or idle....when i maintain constant speed also will jerk and exhaust sometimes will also sound "bob bob" like it does during idle..... when i accelerate and boost, it will like my engine running too lean and car jerk for a while, i dunno why, my car have tuned using emanage blue just 1 month ago and if a/f ratio already too lean, why i can boost here boost there in this 1...