I have a 1986 trans am it originally had a 305 tpi before I took the motor out I went to a performance shop and had a muffler put in with rectangular tips the piping from muffler to cat is stock, I then replaced the engine with a '89 350 tpi and have slp headers with cat now the problem I have is the exhaust makes a funky noise when you get to like 5k and above to try and describe the noise is like a humming noise with metal why doesn't my magnaflow sound like the rest of the youtube videos with similar set ups I currently have posted for sale my cat back to go in a different brand of exhaust I like magnaflow but this us a disappointment to me

 

I have a Magnaflow (2-1/2") 2 in 2 out that I'm running.
I have no strange noises.
Maybe pull the muffler to check if something has come loose internally.

 

Thats what I'm thinking i know magnaflow has lifetime warranty maybe I should have returned for a new one

 

check your heat shields.

 

How is your cat? They make a big impact on exhaust sound.

 

The heat shields are not lose

 

I checked the cat visually , it came with the slp headers I bought off craigslist supposedly its a high flow cat it is bigger in size compared to a stock one wich I have and the insides are still in tact

 

Is it possible something was dropped and fell into the exhaust during your engine swap?

 

What size intermediate pipe you running?

 

It is posible but I'm prety sure nothing that could obstruct

 

Everything is stock, the muffler to tail pipes is aftermarket + the headers

 

I found the issue is the rubber hangers on the rear and the one that's on the transmission are dry rotted and make it hang lose and is rubbing somewhere over the axle and thus making that wired noise i hear

 

Thanks for the up date and letting us know what the problem was.