Question about possible valvetrain problem

[OreoLT1]

I have a 3.8 Camaro M5 with some computer enhancements and other mods. Before this problem occured I was able to run through each gear up to 6 grand(redline) with no problem, now as I approach 4800 rpm's all the way through to 6 grand there is a moderate to loud humming sound coming from the engine. I thought that it may be a problem in the valvetrain but I want to hear some other opinions. Any help will be appreciated.

[98Camaro3.8]

What does it sound like? How fast is the thumping? Does it change with engine RPM? Does it do it in neutral, or only under load? When did it start? Did you do a mod to make it start doing this?

[OreoLT1]

It sounds like a cross between humming and a slight growling sound. It sounds like to me that reaching the high rpm is putting too much stress on some component. It's not so much a thumping sound just humming/growling and it only does it around 4800 rpm and higher to the redline. It does not do this in neutral only under a load and it started about 2 months ago(est. 500 miles ago). I started hearing it around the time that I replaced my ign. coils and added an MSD DIS-4 box. The coils that I put in were MSD Blaster coils and I still need to upgrade the plug wires. If you need anymore info just let me know and thank you for your help.