so my service engine soon light came on and advance auto said it was the downsteam o2 sensor. what im thinking about doin is cutting the cat out and put a custom exhaust in from the headers back. i want to get rid of the downstream o2 sensor and was wondering what type of programmer i would need to do this is it one of those you have to send in to get done?

 

well first thing it's illegal to cut the cat off of a 96+ car! then ur motor will run rich and ur gas millage will go to ****! just replace the 02 sensor there only 60 bucks

 

so if i do a custom exhaust will putting a high flow cat on trip the engine light

 

its a 50/50 thing with the magnaflow one just stick to a standard cat and 2 1/2 pipes and a good flowmaster super 44 muffler!

 

Yeah, if you're running a 2nd gen Blazer, modern day cats aren't too restrictive anymore. I'm still learning on these vehicles, so IDK if what I'm about to say applies to these trucks since they have a pre-cat and a regular cat- but I know on LS1 F-Bodys and 'Vettes (and even on 3.8 F-Bodys), hi-flow cats only show a gain of 2-5 RWHP, and straight piping the cat nets about the same figure. If the 4.3 is the same as those engines, then IMO its not worth the cost of buying the cat or pipe, welding it in, and replacing the O2 sensor or buy an O2 simulator, and the sims only work 50% of the time. And with the HP gain (or lack thereof) in mind, it'd be cheaper and probably a better option to just replace the O2 sensor. So unless you plan on forced induction, heavy internal work, or and engine swap, and loads of money going into this thing for race purposes, you will never notice that small of a horsepower gain.

Just my $0.02 and like I said, I'm still new to the 4.3l world haha. I could very well be wrong.