another question, i have searched ,94 6cy path 4x4,for a custom exhaust what is a good size for pipeing 2.5 ?? and for a ecu chip/where??

2.25 or 2 1/4 is good. With our engines you want some backpressure to help with torque.

As for ECU chips they are a bogus item. They do nothing to improve the performance at all. They monkey with engine sensors and screw up your engine.

I have dual 2" pipes from the cat-back. No muffler. Pretty quiet at idle. The stock exhaust pipe size is 1 7/8, which is no longer manufactured.

As long as you keep a cat you'll be fine on backpressure. You can either keep the cat or the muffler. If your going with a full "performance" exhaust. Well, there are not any power gains except for sound.

In the exhaust system power gains are created by opening up the system while keeping your backpressure within limits.

I used 2.25". See my post in your thorley thread. Yeah don't mess around with the ecu. If you want some real power, go get yourself some nismo cams and do your exhaust and intake. I wouldn't go any larger than 2.5" dia. for the exhaust, and don't go wheeling around water if you buy one of those cone filters. I've heard of people getting water in the engine just by going through a shallow puddle at speed.