Hi I have an '89 Firebird formula with the LO3 TBI305. I just got my 2.5 in and out flowmaster muffler form Summit, and I know my cat is a 2.25. inch one, so I just ordered a (non-mandrel bent) 2.25 intermidiate pipe from dynomax. I noticed, after recieving the intermidiate pipe that the flange is flaired were it bolts to the cat. Is there anyway that I could order a (mandrel bent 2.5 pipe) from dynomax and have it bolt right up to my 2.25 cat. If this would work, I wouldnt have to put a 2.25-2.5 adapter on the muffler to pipe conection. Could I get the 2.5 pipe, or am i just gonna have to stick to the 2.25 I have? Thanks!
Ben

 

I would recommend returning everything you've purchased and starting over. What you've got is barely an improvement over stock, certainly not worth what it is costing you.

Get a 3" direct-fit '86-'90 TPI single-cat, and have it adapted to your y-pipe. Then get a cat-back for the same application from the manufacturer of the muffler of your choice. That will give you a noticeable improvement in performance, even though the stock manifolds and y-pipe will now be your point of restriction. If you address that in the future, again the same application headers & y-pipe will bolt up directly to the above-mentioned system.

This is assuming your primary interest is improving performance rather than just making more noise.

 

i have to agree, is not gonna help out what you have. i didn't have the cash for the whole catback so i bought it piece by piece satrating with a walker mbent 409ss 3" intermedite pipe. then th two 2.5" tail pipes and then just a muffler from npa to make it all come together.

the pipes themselves are not cheap.
you wold probly best off with a full cat back for 300-375.

 

I appriciate the responses, but there is a slight problem.
The 2.25in. Catalitic Converter is less the 1 year old and it is welded to my Y-Pipe. There fore my Question Is, Can I bold a 2.5.....or 3.0 intermidiate pipe to my NEW 2.25 cat??? I think im just gonna have to keep the new 2.25 intermidiate pipe I have since i doubt i can mate a 3 inch pipe flange to a 2.25 cat.
If you think I can, let me know please,
Thanks
Ben