Hey I have a 97 k1500 it has a crate more with 35000 on it. I have car back flow master. Looking to do other mods like make it true dual, intake, headers, 411 swap maybe a cam throttle body spacers stuff like that. What will make the biggest improvements including mpg

Ok, first off, lets get this out of the way. TB spacers are junk. They do nothing in a fuel injected environment. Same goes for tornado'*.

2nd. Determine what you want the truck to do. Get good mileage or get power? You can have one or the other, but not both. A cam is going to make the PCM see more air coming in and going out, so...it dumps more fuel probably maxing out the injectors and causing more issues.

What are you planning on doing with the intake? This is a Vortec engine correct? There are no aftermarket intakes for the 5.7 Vortec'* that I know of.

Headers are nice. They allow better flow of exhaust out of the engine. But a bigger cam would compliment the headers better. CON=more fuel consumption.

I've heard of people doing the 0411 swap, not exactly pretty to do, and because your taking a 2002 PCM from a 2002(ish) EPA environment and putting it into a 1997 environment, its going to bitch and whine the whole time unless you have HPTuners. There are some devices/modules the 0411 needs to see that it won't see in a 97 platform.

Would making it true dual exhaust do anything? How can I prove throttle response? I guess my main goal would be mpg improvements. What headers do you recommend?

If you do just the exhaust, you might get 1 mpg and a couple ponies. That'* it.

You have to remember, the engine is a huge air pump. If it can't breathe right from the intake down, upgrading the exhaust itself doesn't do anything.

Increase flow/volume starting with the intake(cold air intake) port/polish the heads, increase size of valves, increase opening/duration with upgraded cam, increase flow through headers, increase flow through bigger cats and finally through a bigger exhaust. Yes, that is the order in which you should upgrade. Most people only upgrade the exhaust for a better sound usually through the muffler.

Is there a brand you would recommend you would recommend? Will replacing the can make th fuel mileage a lot worse?

Brand of what?

Replace what? Please, check your spelling before posting.

Will replacing the cam* what brand is good for headers, intake ect

Yes, upgrading the cam can cause MPG to go down. Remember, the more air that enters the engine, the more fuel the PCM needs to dump into it. Bigger cam equals more air, more air equals more fuel to burn. And the PCM sees all of this via the MAF sensor and O2 sensors.

Headers, it really don't matter. You get what you pay for. Hooker, Sanderson, Hedman etc.

Again, I already said, your not going to upgrade the intake. You can modify it so it flows better, but in your case, not really worth the effort. So, don't worry about the intake manifold.

Whats your fuel mileage right now? You also have to remember that winter blend fuels will get less mileage than your summer blends. Ethanol doesn't help neither. Your vortec engine as of now is about the best performance wise with a small block chevy. In my opinion messing with the camshaft and Other mods do nothing but pi$$ off the computer. Headers in my opinion are a waste of money and time with a stock engine. Not really enough to notice a difference in performance.

i would agree none of that is worth the money. none of it is going to work well without being tuned for it and hpt is 600. the best mpg increase i got was going to the mpfi and getting rid of the junk poppets. the vortecs as they get old are kind of known for complicated slow loss of power, so if you have an older one i would get a live data reader and check out things to make sure its running right and check fuel pressure, should be in the 60s. mine had all this and cam retard, which is timing, bad without any codes.