2016 Silverado 5.3, Whipple 2.9, LT headers, cats, 3” Carven exhaust w/ Vigilant resonator and 2 Carven TR mufflers, Pat G online tuning in progress.
Truck ran well with Whipple, headers and stock exhaust with Carben muffler. After changing to the 3” exhaust I noticed a little unsteadinessat what seems to be at single cylinder firing frequency. Very periodic and consistent. If it was just at idle you would almost think it was normal but it stays in as rpms increase. Thought something got pulled loose or maybe a leak but no. Pulled the plugs, all look identical very light color, 0.035 gap. At low cruising rpms applying throttle causes the unsteadiness/chugging to get worse. At one point I could give it throttle at 45-50 mph in high gear and cause a truck shaking misfire blinking CEL. ‘Misfire cylinder 3’. I swapped around some plug wires (Taylor header wires) with no change, still cylinder 3 misfire. Replaced the plug, it won’t bring in the dead miss and CEL but unsteadiness is still there. Replaced the ignition pack with no effect. I’ve pretty much exhausted my diagnostic capabilities. Don’t see anything on the HPtuner scans I’ve done.
Any ideas? Is there any way to troubleshoot DI?

David

I’m wondering about the injector, also. I was hoping to get some diagnostic data on it as checking the injector on a direct injected engine is not quite as simple, particularly with the supercharger mounted.
I will definitely check the compression.

I wish there was an injector unbalance PID like a diesel. Had an experienced DI guy tell me he’d seen the same thing on a CTSV and it turned out to be a DOD lifter. Good excuse to do a cam swap.