I have a new Z51 HTC. I almost have my first 500 mikes. I have it in “my mode” with the exhaust set to the most egressive setting. The sound seems to cut in and out when I get into the higher gears. Is this normal or should the sound be on the louder side at all times?

 

It's likely occuring when the engine enters AFM V4 mode so the valves are shutting. If you use Z-Mode, it shouldn't occur.

 

No matter what mode you are in npp exhaust partially closes valves at certain rpms. This is especially noticable at around 2k which is common at lower speeds where you would be say in a neighborhood area. Only way to avoid it is get an aftermarket exhaust with simulators and no valves.

 

The NPP will have two sets of valves. The AFM valves close whenever you go into AFM (V4) mode. The tailpipe flow control valves are controlled in accordance with the engine/shift setting. Except they will also close when you go into AFM.

It will change tone when AFM (V4 mode) kicks in and AFM and tailpipe flow control valves close. That will happen when the engine/shift is on any setting other than track when you cruise steadily. To avoid AFM you can use Z mode with the engine/shift set to track, or you can use Track Driver Mode. One other way to avoid AFM is to use M shift, then AFM is deactivated regardless of the engine/shift setting.

Although with engine shift set to track mode the tailpipe flow control valves may close sometimes, they are mostly open all the time (except if AFM is activated). I have a hard time finding the case where the valves close in that setting. Tour mode will have the tailpipe flow control valves closed at idle, and mostly closed except when stepping on the gas pretty good. Sport mode has the tailpipe flow control valves open at idle as well, and open most of the time like track - but allows AFM to kick in. In weather mode the the tailpipe flow control valves close all the time.