You can also have or do a compression check of the engine. If your cylinders are all close to pressure and with in the specs, no need for a rebuild.......SFC

 

I would blame the fuel pump. Mine went out at about 90,000 miles, my dad's went out in his firebird at 75,000 miles..... both had the 3.8 V6. It's about $1000 to have a mechanic replace. We did mine myself, and it took about 8 hours. Common problem in the F-body's though. And God only knows why GM didn't put in a trap door or soemthing to make it easier to get to the pump.