GreenMachineButler
New member
I have a 2015 sonic rs and I have read about the power output dipping at around 5500 rpm and mine doesn’t so I was wondering why that might be because I just bought this car, I found the original owner of the vehicle and he told me when it had only 5000 miles on it the radiator cap failed and caused it to blow a head gasket, when he had the gasket replaced he had stiffer valve springs installed and he also had the shop port and polish the head before reinstalling so I think that explains why it doesn’t have that dip in power, it also had the gm performance exhaust installed with the calibration from the original dealer, my question is would I benefit from a wide band o2 sensor before contacting bnr for a tune? I’m sure the boost pressure is different from stock due to the head being ported and polished
