I dont think the H pipe will cure your problems.
Here's a few setups I've run:
If you're looking for low noise dont get the Magnaflow - get a Quiet Flow 2100 from napa (OEM for a Silverado) - here's a thread I posted about my install - I was very happy with the results.
http://www.classicbroncos.com/forums/showthread.php?t=168161&page=3
For comparison, here's a vid of my 2into1 that I did on my blue truck (with the 3 chamber magnaflow):
FYI I used about six feet of 2.5" pipe, two 90* elbows, two collectors and a quick dump for a tailpipe:
[youtube]u98OuHwFWys[/youtube]
I got a lot of drone from this setup so I swapped the muffler for a Walker Quiet Flow 21400 is great! Sounds like a truck again. The muffler is a monster at 29" long.
The sound is way more subdued than the other mufflers. Not whisper quiet (I dont think thats possible) but no where near as annoyingly loud as it was before. Cruising at 40+ and all I can hear is the wind and the tires.
Here's the specs on the muffler:
Cost $120
Body Configuration : Dual Offset Inlets - Center Outlet
Body Diameter : 7" x 9"
Body Length : 29"
Muffler Inlet I.D. : 2 1/2"
Muffler Outlet I.D. : 2 3/4"
Muffler Shell Overall Length : 24"
Lifetime warranty too. Here's this one for comparison.
[youtube]rfUMYvGibRA[/youtube]
Here's the last bronco. Version 1 was mildly built 302 with long tubes and 2.5" exhaust with glasspacks routed straight out the back:
[youtube]tM4sv_RnVNY[/youtube]
I swapped out the glasspacks for Summit Turbo mufflers, added an H pipe and routed the exhaust out behind the rear tires. This one was the best of the bunch - low rumble, not loud...just perfect.
[youtube]njlFsDiG0xw[/youtube]