1) I want headers. I however do not know which to get. In your experiences which brand (part# appreciated). Gave you no problems or very little problems with fitment. Its a 1991 Base model TPI. I just don't want to buy a set and then kick myself in the butt cause they don't clear this or that or don't bolt up to anything behind them. Any full front-to-back kits you would recommend? So what do you guys recommend?

I don't have to worry about a smog test but want to keep cats in the system.

2) Speaking of behind them the highest flow cats I've found are around 613 cfm I've heard that you need 2.2cfm per hp for the engine to see no back pressure. I was thinking of full length headers-->collectors--> Xpipe---Dual high flow cats---> dual pipes---> Mufflers.
Does that sound like a plan? I've built and rebuilt a few engines with pretty good results, but they have always been pull out and put back in or drop in..with exhauxt mostly there already. So I really have very little experience with exhaust design.
Give me some ideas guys..tell me what I should do/not do to have a nice free flowing exhaust.
Theorycrafting is welcome, any advise is welcome and will be well thought about. I value the experiences of thos who have "been there done that...got the shirt.".

 

Obx

 

Get a well known brand that has made plenty for corvettes, starter motor clearance can be an issue (some require the smaller geared starters).
With headers you will get a lot of heat in the engine bay ... do not use exhaust wrap that will shorten their life.

Check the clearance to the floor, headers are great for overheating your feet especially the long equal length type headers, (women wont stop bitching if their feet get hot)
Don't forget to improve the Y join from headers to the main cat ... the standard one is not a good flowing one ... you will see by just looking at that.


You will be pleasantly surprised at the increase in performance
When i went from stock standard to headers i did a 1/4 mile run stock standard it did 14.4 then did another run with headers on it went to 13.6 cold air intake and adjustable fuel pressure regulator got it down further. that was before the blower... v8s love headers

 

 

I'm installing a FirstFuelInjection intake this weekend (I just love the look of a TPI). I have the hotcam kit for next weekend. Looking to do the exhaust the weekend after. Then start data logging and writing chips.

 

I bought some Hookers for about $350 for my 85 several years ago . Can't remember the model number - 2149 or 2151, but these hookers have the emissions stuff and air tubes. I installed myself using jack stands, one side went in from top, the other from the bottom. I can still change out my starter (and the 85 starter is the huge one!) without messing with the exhaust at all. Plugs/wires are easier to get to than the manifolds were. The pipes that came with didn't exactly fit, so I had a shop fab from headers to cat, which had already been replaced with a hi-flow. The cat-back was also previously replaced with pipes that were 1/4" larger than stock, with Flowmaster mufflers and LT1 tips. The headers are subject to a little road rash underneath, might be something to watch out for if the car is or will be lowered. My rear is lowered about 3/4" but I've only scraped the Hookers on the most extreme speed bumps.

I love the sound, it isn't unbearable when driving- if it were much louder it would be though. The motor is all stock, but with a nice cam, it would sound awesome! Again, this is on an 85 so YMMV on your 91 regarding fitment etc.