Just got one for my '97 ext cab 5.4L. I've had a Flowmaster SI/DO system for several years with first the 50series then the 40series. Never a good sound and WAY too quiet, plus in-cab drone @1800-2000 rpms. Decided today at @50,000 miles to change the converters. Took off the 4 and had 2 highflows installed. Left the 40series Flowmaster intact for now. DRAMATIC difference! It has some real low speed GROWL now. I don't have to floor it just to know it's running now. This sound is alot closer to my old '91 Z28 with the 350tpi and Flowmaster 3" exhaust and headers. It has a slight pop when letting off and the drone on the freeway is toned way down. Almost perfect in my opinion. I can actually hear the exhaust coming from the rear of the truck instead of under it. Only problem is it still gets quiet cruising when not giving it gas. But idle and low speed are great. At $260 it wasn't cheap, but by far, the best mod I've done. So don't waste your time changing mufflers over and over. Change your converters FIRST-then choose a muffler. It's the only way to hear the true potential of any muffler.

 

Who did the work? Did you have to look for a place to do it or did you have already high mileage? What did you do about the other 2 O2 sensors?

-AR

 

Jackal-no problem finding a shop to do the work. I was only @40 miles from hitting the 50,000 mark. I was always told that in Ga you had to hit that mark before touching them. I told my shop what I was looking for sound wise and they suggested the highflows. He said changing my muffler again with stock converters was a waste of time because the amount of air entering the muffler would still be the same. As for the O2 sensors, nothing was changed. The shop said they were not allowed to change the location of them. They cut the pipe just after the first sensor, removed both converters, then installed the highflow with a new piece of pipe to make up the difference. This was attached to the second sensor still in original pipe and same location. I plan on getting either a new y-pipe or running true duals with an x-pipe later. They said I would just have to cut the pipe after the second sensor and before the stock y-pipe.
After driving it now for a couple days it is totally different than running the stock cats. The cab is alot quieter now. All the sound comes from behind the truck. Drone is basically nonexistant now. I guess the stock cats hindered the flow so much that they were what was resonating. I even find myself driving slower now because the low speed sound is so sweet!

 

...you only have 2 cats. Must be nice.

-AR

 

hey Knight, have you got any details on the manufacturer of the high-flows? I've been looking for some for a while now and every exhaust shop I take it to says no such thing exists.

 

Like Matt looking for more info on the availability of those units. Do they have a site? Keep in touch. And thanks for the details.

 

If you call summit Racing they can tell you what cats to go with. My Muffler shop and Summit both sell only Catco brand cats. I have a catco on my motor home and love it! My cat was only $50 Compared to $130 the muffler shop tried charging me.

 

Trigger

Are those high performance or just OEM's ?

 

Catco's are performance cats which are better flowing. Definitely worth the $$.

 

TakimanPGT

Where can I find those?

 

Try this
http://www.discountconverter.com/dealer.htm

 

Sorry I haven't posted any more info, but my wife's grandmother has been in bad shape for a few weeks and actually passed away on Wed. All I can see from the bottom of the converters are an arrow showing flow direction. My paperwork just says "removal of converters and installation of 2 1/2" highflow units". So I'm not sure of the brand. I don't think they are application specific, just universal. I used to run Random Technology Super High Flows on my '91 Z28. They are rather pricey though.

I have driven the truck for about 300 miles since the converter change. Today I was leaving the recycling center which is positioned in a bad curve. I always have to ****-and-git so to speak when I pull onto the main road. Before the change the tires would only break loose midway through turn in onto the road.But today they broke loose as soon as I hit the gas and kept spinning after the turn and alittle after I straightened up. So I decided to check her out. I pulled into an empty parking lot and stopped. From a standstill on level pavement I left about 4 foot of black mark! Very rarely could I break them loose before and then it was only a small chirp. Perhaps lowering the backpressure on our trucks isn't as bad as some say!