I have a 3.1 v-6 in my 99' monte carlo. Im looking for the best choice for upgrades in the line of sound/hp. so if anyone can help plz do..thanks

 

First you should do a Fender Well / Cold Air Intake. i have directions here: http://www.cardomain.com/ride/473859/6
this will make the sound much deeper and give you a good amount of power you can actually feel.

IMO i think the best mod for you is to do an intake manifold swap. go out to a junk yard and find any GM car with the 3400 v6 the intake manifold will look a lot like yours (cause it basicly is Just BIGGER inside) just put that manifold and the new TB in your car and bam! next either get headers or at the very least replace the stock mufflers and piping from the Cat back.

after these your next mod should be either a PCM chip or if you plan on doing more mods later a programer. DigitalHorsepower inc (DHP) makes these for your engine.

later on? its up to you.
but a short list is:
-cam
-Pulleys
-heads
-ect....