This is the terminology that plagues the our community. Two things mean differently to different people. There's no right answer because it's so convoluted, but my common understanding is this:

The "Fister" mirrors the muffler modification done by Mr Fister / FD Motorsports which welds in a partial bypass to the stock muffler -- https://fdmotorsports.net/shop?olsPa...t-modification
(I was not interested in shipping my mufflers across the country so I had a local shop perform the same mod)

The Gundo term has been around for years and is the "original" stock muffler hack to mirror what the PSE muffler is at a fraction of the price.

The only internal muffler modification is to cut the muffler open and remove all baffling. There is not a terminology for that besides maybe calling it a "Fool The Feds" mod. If you're going to go through that trouble, buy the $100 ebay muffler deletes and enjoy the weight savings (and drone)

Hope this all helps in your decisions

 

Someone PLEASE explain ..... Fister (or Gundo) is the short pipe welded from the intake to the exhaust side of the muffler....what is the "other" mod called, the one where the "sealed "port" at the other end of the muffler is opened and a pipe run to the exhaust side of the muffler???

 

dak911

Look at the photo Vipertag313 posted showing the Fister and the Gundo mods. Notice the bypass pipes - Fister and Gundo are two different designs. When the sealed opening is removed, it is the Gundo mod.

 

True. I call mine Gundo even if it’s not 100% correct.

My first thought to respond to the OP was “do a search,” as there are many threads on this topic. Possibly dozens.

I had a welded pipe bridge the gap between the intake and exhaust portions of the muffler. Total cost = $200, although I did the labor myself (remove rear bumper cover, disconnect exhaust pipes from the cats, pull rear wheels off the car, and then remove the mufflers - take them to a welder and explain what you want).

 

Boy am I glad I bought a car with the factory exhaust bypass setup. Love the sound and none of this confusion.

 

There are so many different "explanations" hopefully you are right...I have heard the "bypass" (short pipe between the inlet and outlet called "GUNDO"
Can someone explain the difference in sound between the "by pass...Gundo ?) and the Fister ...(opening the "sealed" opening"?
The only muffler shop here I "trust" wants $350 to $450 to do the "by pass" (want's to see how long it takes)

 

I also did the Fister mod. Great sound that's quiet at idle (once warm) with deep throaty sound accelerating. It costs more, yes, but the results are great. My mufflers also had some cracking so those were repaired at the same time.

 

Listen two the two videos posted above, that's the best description you can get!
You shouldn't pay more than $200.-$250.00 for a shop to do this.

 

VIPER...

Did you lose any low-end torque when adding the x-pipe with the Fister mod?

 

Quite a bit of low end torque loss. It's noticeable. However, the top end is a very strong power gain. I love the sound so I don't mind.

 

Thanks for the feedback. I'm looking at whats best suited for my Fisters without losing power or torque. I'm looking to increase performance and sound as a secondary but I'm not sure if I should go with or without cats on x-pipe or crossovers.

 

I found a small mom and pop shop where the guy would listen to me and look at pictures I supplied from this forum, put my car on a lift and did it all for $150. The tail pipes weren't quite right so he put it back up in the air and got them adjusted to same heights. He wanted to charge me $140, but I splurged and gave him $150 for going the extra mile. I didn't have to do anything but touch ATM buttons.

 

@dak911

First photo below shows actual the 996 muffler with the Fister cross-pipe.


There are a few versions of the welded in inlet/outlet cross pipe. Fister locates and TIG welds the cross-pipe on the engine side of the muffler just above the mounting bracket and many local shops locate it on outside/bumper cover side of the muffler and MIG weld it. Locating it on the bumper cover side places the cross pipe very close to the bumper cover (heat) however there is insulation inside the bumper cover.

The Fister design and welding is clearly the least visible and best, however the mod is not visible outside the car so perhaps it does not matter.

 

This exactly correct. The gundo (PSE style) is what I have and you can barely notice the difference with the stock exhaust. I have serious doubts about that theory that says that just welding the third pipe, you make the muffler sound like the PSE. I think the PSE must have different piping inside the muffler to bring the gas to that additional outlet. Did anyone ever open a PSE muffler and a regular muffler to see the differences? Any video comparing a stock PSE sound with a Gundo hack mod?

The Fister mod, is a bypass and obviously it sounds louder, I dont like it too much tough (just personal taste here). I like the sound of the factory PSE (what the gundo hack, I think doesnt approach)

The problem with the attached videos, is that the one with the Gundo mod (PSE style) has also a XPIPE, so you can not say if the sound is because of that.

 

Has anyone ever done any before and after dyno testing to see if there really is any power gain/loss? I'm not sure how you would have a drop in low end torque just by bypassing some exhaust gasses? I'll be doing this in the next week or so.

Kyle