How to remove the exhaust manifold along the firewall

[javelinmania]

I have a 2007 Quest that I bought at auction and it had a lot of error codes. Took off the intake manifold and replaced the plugs, coils, cam shaft sensors and other stuff. Then I went to replace the Heated O2 Sensors. Found the front one and replaced it. Couldn't find the second one. Then I discovered that the Cat had been taken off and a straight pipe put in its place. I've been trying to get the two bolts that go up into the exhaust manifold off. I have tried penetrating oil, I have tried Heat and I'm beginning to round the heads on the bolts. I'm starting to think I may have to remove the exhaust manifold which will probably have the same issues.

Suggestions? Tips?

If I have to pull the engine I might as well get a JDM engine.

[AZhitman]

I'm of the opinion the takeout motor might not be a bad call. Snatch your new parts off the current motor and minimize your agony. God only knows what other janky "repairs" you may run into.

[javelinmania]

3 of the 4 bolts holding the fake catalytic converter are now removed. I've been soaking the 4th and hitting it with an air hammer trying to get it loose. Hopefully tomorrow I will have it off. I may be able to hold off on the JDM engine - unless I find something else.

[javelinmania]

I finally got the 4th bolt off. Once rounded the head of the bolt I knew it would be a real pain. I took off the right axle to give me more room (which needs replacing anyway) and went to town with drilling, grinding and using a cutting wheel. After multiple days I got it out. Now I need a few days to recover and I will attach the new catalytic converter on.