I'm getting ready to change out my cat and muffler and I need to know the size of the pipe. It'* freezing cold here in wyoming and i haven't felt like crawling underneath to check the size. Thanks for all the help

Not to sure if this will help but I just had my exhaust changed.

Sorry, but the cat model name and size escapes me. The supplier knows, just tell him the car model and year, they'll know.

The pipe length before all the bends is about 12 feet. We have the same year so I assume the length is the same My system is all stainless steel. You have a choice on pipe diameter 2.5" or 3"...Hector and the other "pros" can provide more expert information.

Hi flow cat converter cost $258 CDN installed
12 ft bent stainless steel exhaust pipe, Magnaflow muffler and tip totalled $712 CDN installed.

Its not much but its a start!!

Hmm.... I dont know, the 88-91 Bonneville years made low HP but modern torque. I wonder if a 2 1/4" pipe would do better for those years? Either way. And too little backpressure probably wont cause burnt valves. Rich or lean (I forget) can cause burnt valves, not burning all the fuel (bad spark plug) lots of reasons.

Good call on the low HP, its disappointing only 150 on the LE and 165 on the SE, however, a new exhaust will jump it up 10 to 15 HP. Off the bat it is very noticable once the new system is installed.

As I mentioned to Hector I believe my pipe is 2.5". But 2-1/4 is the best bang for your buck. I want to confirm with my muffler shop what size they used.

I'm putting on a new muffler and was just wondering what the stock pipe diameter is? 2",2 1/4?

There was a big jump in HP from 91 to the 92 years. So you know where it came from.

I will let you know when I look at the internal design of the 88-91 Bonneville'*.

If I went with 2.5 all the way through with no cat, would this be bad for the engine?

oh yes...

Back pressure is a good friend. High flow performance cat is a good upgrade, and its good for the environment (my green thumb for the day )

I had the factory sport or performance exhaust, it was low grade stainless steel with the double tips. They pointed downwards which was lousy.

After 14 years the low grade SS rusted out and now its high grade SS performance, the Denali tip is cool.

Where would you find a stock 91 sport exhuast? Are they still made?