I have a 06 gmc lbz, Aftermarket parts: Edge cts 2 programmer, S&B intake, Mbrp straight exhaust, air dog 2 fuel pump. Over the last couple days I would lose power and look out my mirror and tons of black smoke. Hit the gas and it eventually cleans out and runs good. Cleaned the air filter, cleaned the maf sensor. Still doing it. I'm thinking egr issue? I did get a code p0405 egr position sensor circuit low voltage. Any ideas? Thanks in advance.