I was wondering if anyone knows how much backpressure you should have on a 95 4Runner 3.0 . I have 10 pounds at the right manifold, 5 pounds in front of the cat, 4 pounds in front of the muffler. The readings were take at WOT at 4000 rpm.

This just seems like a lot to me.

 

I had mine checked a while back (only in front of the cat) and it was about 4. The guys at the muffler shop said as long as it's under 5 (in front of the cat) you're ok. I'm not surprised by your high reading at the manifold. The stock crossover used on the 3.0 is an engineering disaster IMO.

 

If you install headers on the 3.0L engine - on a 4 runner
does it eliminate the cross-over pipe or does it cause other problems ?

My runner has never had a Cat - previous owner removed it.

 

Yes. Headers will eliminate the stock cross over. If you install headers you will go with a different cross over all together. Mine crosses over under the transmission and is much less constrictive. One could argue that having a cross over hang down by the tranny would result in damage to the pipe from rocks, etc. I have had mine down thier for over a year now and I do a lot of wheelin' with absolutely no problems.

Even if you do damage it, it is cheap and easy to fix.

 

That's great news - did the headers make a big difference in power ?
I have a brand new engine that replaced my 215,000 mile motor -
$2400.00 later it runs like it always did. Just don't use any oil.

I've read that the cross-over pipe robs lot's of power.

 

Headers will make a considerable increase in power. Downey claims thier headers will produce 11-14 hp. depending on the rest of your exhaust system. Putting headers on the 3.0 is a very difficult job to do yourself. If decide to go with headers, I recommend going with the ceramic coated ones. Also, when setting up an exhaust system on the 3.0 be carefull not to go with too much freeflow. You will end up losing low end torque.