I have seen many posts about how to tune our engines to either get more HP/Lbs or get the best gas mileage. Well here is some things that have helped me out, mostsuggestions have been mentioned before. I drive about 100+ miles a day for work and have to exspense my mileage so I keep meticulous records. My Blazer is an '05' 2dr 2wd 5-speed with 25k miles on the clock, only mods I have done is free up the exhaust cat-back and add K&N air intake system. Since new I have used Castrol Syntec and Pennzoil Platinum synthetic oils. After doing some research on synthetic oils online on such websites as http://www.amsoil.com/performancetests/g1971/index.aspx& http://www.performanceoilnews.com/oils_against_oils.shtml. I decided to try out Mobil 1 Extended Performance Full Synthetic oil. After 3 full tanks of gas I have noticed smoother idle, better offline pickup, and 1-2mpg increase on my mileage. Not to mention itis guaranteed for 15,000 miles before next needed oil change. I have a few friends that work at the Citgo and Exon-Mobil plants as engineers near my house. They both swear by Mobil 1 synthetic oil. They also said "we used to have to tear down and rebuild our test engines every 15k miles to keep accurate and fair data. We started using 'Chevron Techron Injector & Fuel system cleaner and havent had to rebuild the enigines yet after 100k+ miles." I have heard many people before say good things about using Chevron Techron in cars to keep them running smooth. I have used it in some of my past higher mileage cars and noticed the idle and mileage clear up.
People with 100k+ miles on the odometer obviously want to make sure they have fresh spark plugs, wires, pcv and egr valves, and possibly new O2 sensors. As well as fresh antifreeze coolant because a cooler engine runs better! :)
The only other mods I know that will free up hp/torque and add better gas mileage is electic fans, pulleys, and ecm/pcu flash. word of advice, Hypertech III programmers, Superchips, and Jet power programmers do not add better gas mileage because they only advance the timing and firm up shifts. A computer flash gets rid of the 'torque management' set by GM and allows the 4.3 to run at optimum level in the low-driving rpm range thus getting better gas mileage. I hope this helps out people that had questions about getting more HP/Torque and mpg out of these 'workhorse' motors. Let me know what you guys think

Peas

Where can I get a flash from?

Thanks.

There are numerous online PCM tuning sites. PCMforless.com comes to mind for one.

On the oil sites listed above... Well, they are a bit lopsided... Both are funded by Amsoil. For some good, unbiased sources, head on over to the forums at Bobistheoilguy.com (http://www.bobistheoilguy.com). As far as oil increasing your fuel mileage... Well, I have never seen anything as dramatic as 1-2mpg increase out of any of the vehicles I have switched. And this includes my old '00 Bravada which went to M1 5w30 for 10k, then back to dino for 3k and was on M1 5w30 for the last 10k that I owned it. I switched back to dino because I had a leaky pan gasket which turned out to be loose pan bolts. During all of that time, I never saw any real change in the mileage that could be attributed to the oil. As far as the extended drain periods of the oil... Well, I would still recommend that you change the filter every 5-6k miles.

Now, onto some of the things I would contest in the original post... The Blazer does not have torque management in the sense that the PCM is cutting power output in the lower RPMs.

You can get a decent gain in fuel mileage with a hand held tuner. Problem is, these tunes are a bit more conservative than a PCM tune, but even by sending your PCM out for tuning will be more conservative than a full on custom tune.

Typically, a PCM tune where you send your PCM in for tune will be cheaper than the hand held units. Thing is, you have to deal with the down time, or pay for another PCM. And then you have to have a case-learn done. With the hand held tuner, you can tune it, change things, and remove or change it when your needs change. If you sell the vehicle, you can return it to stock and sell the tuner separately. If you go in for warranty work where they rewrite the PCM, you can rewrite the custom tune back onto the PCM afterwords. Try that with a mail order PCM tuning company... Ofcourse, if you find a shop locally that'll tune, then you get the best of everything.