Rougher with Header?

[launieg]

I just had Vick's header installed, along with rest of the rest of the exhaust system. So I've gone from stock '81 FI system to the header, 2.25 inch pipe and a matched muffler. Okay. I think I like the header - a little more hp maybe, and certainly the leaks in the old system are now gone, and the cat too, as well as the patched muffler. But it is now too loud for my liking, although a nice note. So I'm going back to the shop for a resonator to be inserted where the cat used to be. But, in the meantime, it now seems to have a slight tendency to miss when starting out in low gear - just brief and then fine. What could have changed? (It did get a new O2 sensor with the install.) Also, (without previous experience with a header) is it normal to have that "sort of backfire" sound at the muffler at times when I take the load off the engine? (I know I should know what that is, but I can't recall - yikes, gettin' old.) Do I now not have enough "back pressure", or is that a bs concept?

[launieg]

Just realized that I should check the timing. I bet they bumped the distributor a bit!

[AndyVAS]

These cars should run smoother with the header and full exhaust system. It all helps keep up velocity and increases scavenging between cylinders.

[launieg]

Thanks Andy. Good to know. I am working on it, and also the muffler guy. I suspect we can see the proper results. I'll post when in a day or so, when it is fixed.

[ORFORD2004]

is it normal to have that "sort of backfire"

Check your throttle position sensor. Need to be OFF(no contact) when gas is release.