I have a 2000 Buick Le Sabre 3.8 V6
 

I recently replaced the upper intake manifold due to it exploding, after replacement, the car ran but would die within a few miles, I have also replaced tha IAT, MAP, and MAFS, but now the engine will start but die after a couple seconds. Does anyone have any suggestions for where to go next with it?

Did you address the likely cause of the explosion, the fuel pressure regulator? I would also check fuel pressure in general.

fuel pressure is excellent, I was told it was a bad MAF sensor, which I have replaced

normally get codes for maf if its that. alot of times if you dont get codes it either the crank position sensor or icm. crank sensor is very common on that. see if you are getting spark when it dies

What do you mean by exploding?

There is a video where the f/p leaks fuel and is ignited by a hot engine.....

However, there is also the possibility of a bad cat......

I have seen customers drive their vehicles with a bad cat, the back pressure gets to a point where it can unseat the EGR valve and you have unregulated hot exhasut gases come into the plenum,,,,it gets so hot, it will blow a hole directly over the stove pipe(part that sticks up from the lower intake and can cause coolant leaks if it contacts the plenum), in the top of the plenum.....

The fuel pressure may be fine, but normally a faulty fuel pressure regulator is at fault, if not that the o-rings on the fuel line at the back of the motor tend to leak after a while, I could see that starting a fire, not sure about an explosion though.

Is this how yours exploded?


Watch this video, at the 1:50 mark shows how to test for a ruptured diaphragm on a fuel pressure regulator.

I don't understand what the good situation ? if the fuel get out or not ?

If the fuel is leaking out it is bad ...and needs immediate replacement.

There is no good situation that comes from a leaking fuel pressure regulator, for a possibility see the first video I posted with the upper intake exploding, that is one of the things that could happen, most of the time I believe it will just run a bit rough, plugs could become fouled.
Replacing the fuel pressure regulator would be much cheaper then dealing with what could happen.

Exploding Plenum
 

This is caused by the fuel pressure regulator. I just replaced my plenum again because it exploded (photo 1). The first time I replaced it was because of a coolant leak (about a gallon a month). I will post a few photos. I had to replace the plenum, fuel rail, fpr and two injectors. The fuel rail because it was bent during the explosion (photo2) and injectors because they had cracked nozzles (photo3). When I pulled the old regulator out of the bent fuel rail it was full of contamination (photo4). If your car hesitates and kicks while you are accelerating uphill at 55-60 MPH it could be a sign of a bad fpr. I say this because my car did that before and since the repair it has stopped. If you have a bad fpr I would replace it right now. Also if you are doing this repair after the explosion, don't forget to look down in the holes on the LIM and check for shrapnel. Mine had several pieces of plastic in them. Instead of pulling the LIM and re-installing which was a pain in the back the first time I did it, I just modified my shop vac and sucked all the pieces out. I paid $25 for a fuel rail off of a Riviera and $15 a piece for the two injectors, they came off of a 2000 Bonneville. I figured a new fpr was the way to go which ran me $62 at my favorite parts store. I think the car is running better than it ever has for me.