Motor running stange after an h pipe install?

[Yo!]

Hello everybody!

Seeing if anyone could provide me with some insight.

This weekend I knocked out a few issues with my truck that needed to get done. It's a 91 Blazer with a carbed ZZ4, 1406 performer, MSD6A, Super Billet dizzy w/o vacuum advance, headers, true duals.

Here's what I did:

1. Find switched 12v for choke
2. Fix leaking intake manifold bolt
3. Install H pipe

After I did all these things my truck is low on power and seems to be missing off the line. Power after the 1-2 shift is sucky at best. I'm thinking I either introduced a vac. leak when I was messing w the intake, or I choked my exhaust installing the H pipe. Power band as a whole is erratic but gets better as the motor warms up. I got the electric choke working, but disconnecting it produced no changes. It's not a choke issue. Truck seems to warm up a lot faster since I've done the H-pipe?

First thing is first, I noticed the truck miss and pop off idle; I had plug wire arcing issues before, but solved the issue by upgrading headers, using 90* boots, dielectric grease, and high temp wrap. I have since checked all the wires and all are ok with no sign of arcing. But I swear the truck "popped" when it missed, just like an arced wire. I ordered a new cap and rotor for good measure since mine was old as balls and a little crusty inside.

The idle is nice and smooth at about 600 RPM after the choke opens, so I don't know if I'm dealing with intake vacuum issues or not. I installed a Performer RPM about 4 weeks ago, and noticed that there's a tiny bit of coolant coming out the back. I pulled the 2 most rearward bolts on the passenger side of the motor (Bolts # 5 and 6 on the torque sequence http://www.edelbrock.com/automotive_.../7000/7101.pdf), put some sealant on the threads, and re-torqued to 25 ft lbs. Could I have introduced a vacuum leak here? I used a 1/4" layer of RTV at the front and back of the manifold during the install. Can a leak at the front or rear of the manifold introduce significant vacuum loses? I wasn't sure if manifold pressure exists in the intake valley or not.

I'm also concerned that I created a bottle neck with the H-pipe install. Pipes are true dual 2.5", but I didn't use 2.5" T-fittings to add the pipe, I simply notched the pipes and welded in a 2" H-pipe. I chose a location about 12" in front of the mufflers, right behind the Tcase. Do you think that I could have choked the exhaust by using a smaller tube H pipe, or perhaps from blockage from welding in pipe at a notch instead of using the appropriate t fitting?

Finally, I didn't unhook the battery before I welded on the truck. I know, I know, I usually do it on other people's cars, but not mine. I figured since it's a non ECU engine and since I grounded 6" from my work, it should be ok, and that's been the case for years welding on this rig. Just throwing out any and all potentials here.

Anybody have any other suggestions or comments?

Much obliged!

[motornut]

....where did the choke power come from
hope not the dizzy

[BigBlocksRule]

Uncork the headers, that'll tell you whether or not it's in the exhaust. Sounds like an ignition issue to me, though.