Thread: 99 GTP: SLP or MagnaFlow?

Hello everyone, My car is in storage for the winter and im thinking when it comes out in spring, i want to upgrade the exhaust, due to the previous owner doing a hack job muffler delete, I want a legit setup. These are the 2 options im choosing between:

The SLP PowerFlo: 1997-2008 Grand Prix PowerFlo Exhaust System - Dual/Dual Tips - slponline.com

OR

The MagnaFlow Street Series: MagnaFlow Pontiac Grand Prix Street Series Cat-Back Performance Exhaust System

Now I want an exhaust that sound deep, loud, minimal drone and looks the most period correct/OEM, does anybody have either of these systems installed on their GPS? Thanks!

All I know is: Don't delete the CAT or the resonator (you can use a glasspack in place of the res.) and don't install chambered mufflers. Also, the stock catback is good for up to around 350HP so no power gains to be had from a different catback.

From a previous post: For power, you'll want headers/PLOG and DP.
Those will also deepen the sound of the exhaust, and barely make it louder. Deleting the resonator wont net any power gains, and will cause it to be extremely raspy with aftermarket mufflers, and drone like crazy with loud mufflers.
Mostly for sound, you'll be wanting mufflers. Consensus for the 3800 is Borla XS. I run headers, 3" catalytic, stock cat-back but with Summit turbo mufflers. Sounds good at idle, but is nice and quiet above 2k.

There are plenty of opinions on this subject, so do some google searching and see what comes up. The 3800 sounds like crap with the wrong combo of exhaust on it.

Both of those setups are going to be annoyingly loud. As said above, you may want to add a resonator to them to quiet them down.

Damn, at over $100/ea for a res on a stock GP seems pointless. For that much I would invest in mods that would actually make the car faster.

Deep, loud and minimal drone is not possible on the 3800 last I checked. If the OP wants that then I would likely suggest and F-body swap.

I agree, But honestly im not looking for power gains, just a legit setup. I did some google searching before this and vids are either just mufflers or have other mods (Cam/headers), was just wondering if anybody had a setup just with the exhaust. Thanks for the opinion!

I have the SLP Powerflo catback on my GP with catted SLP headers '04 SPO tips. I've had that setup for about 14 years. From my personal experience (keep in mind this is with headers and the thicker walled spo tips) brand new won't be much louder than stock. After putting some mileage on the system it will get deeper and it will be on the louder side in the higher rpms. As far as drone you can expect some in overdrive on the highway, but nothing that will make you pull your hair out. A few years ago just before my daughter was born I put an SLP Loudmouth II on as a resonator and now its perfect. Virtually no drone and definitely mellowed out the sound a bit.

One thing to keep in mind with the SLP is that you have to drill a hole in your rear crossmember to move the exhaust hanger from the stock location. I personally think its the best bang for the buck on a do it yourself system and mine is still solid after all these years.