GM Truck Club
Founded in 2004 ~ We're the #1 Chevy Truck & SUV Forum.
Silverado & Sierra | Tahoe & Yukon | Suburban & Yukon XL | SUV & CROSSOVER
Results 1 to 5 of 5
  1. #1

    Default couple questions on 89 5.7l

    i just baught a 89 1500 5.7l thats in excellent shape. im looking into getting a exhaust from the cats back and a intake and was wondering what you guys reccomend, im mostly aiming for better gasmilage(drive 50 miles to work everyday) i can get walker ones pretty cheap but im looking for something that will give me the best milage. also when my truck is idling its pretty rough, the idle will go up and down a couple hundred rpms, not sure what it could be from

  2. #2


    Well I could probably say that the some more information is needed.
    What part of the world do you live in, eg... what type of weather patterns will you be experiencing.
    How many miles on it.
    What's your preference for fuel.
    2X or 4X

    The more you can help us, the better we can help you.

  3. #3
    Sr. Engineer
    Join Date
    Dec 2011
    11-22-boogie woogie avenue


    HELLO IVETO. Actually there is no exhaust you can get to improve better mpg,s .. would like to invent one .
    Make some money huh lol
    I have flowmasters good exhaust ..last forever ..sounds good . if you want a good rumble get a 40 series.. but if you have inspections might not pass.
    50 series sounds good mellow .. one i run.
    On the running issue.. check for vacuum leaks .. around throttle body ..lines ect. check pcv valve .
    Might be iacv/ idle control valve... screwed into passenger side of tbi unit . has a big plug with 4 wires . might take out and clean port.
    Also could be 02 sensor .are you getting a check engine light?

  4. #4


    i live in pa and we have 20-100 degree seasons. i prefer unleaded regular (around $3 a gallon where i get it) its a single cab long bed 4x4 70k on the motor. im mainly looking for something that will give me good milage not concerened about performance at the moment. i heard free flow cats will help with an intake and eventually get a tune when i get time. any help is appriciated

  5. #5


    Moding for mileage never seems to get the results people expect. The new cats will only improve your mileage if your old one is fused blocking exhaust flow. When I tried the Edelbrock manifold on my old 91 K1500 I didn't feel any power increase so I doubt it'll improve mileage. The only surefire way to improve mileage is to run the skinniest tire you can at the proper pressure, use cruise control as much as possible, avoid jackrabbit starts, and drive as slow as is safely possible.

    97 Chevrolet Suburban K1500 5.7L
    78 GMC High Sierra K1500
    Fat, drunk, and stupid is no way to go thru life.

Similar Threads

  1. Couple of questions?
    By Jonathan Lister in forum Chevy Silverado Forum (GMC Sierra)
    Replies: 13
    Last: 08-18-2011, 01:48 AM
  2. New here from CT, have a couple questions:
    By Zbyler in forum CT - Conneticut Chevy Truck Club
    Replies: 4
    Last: 02-09-2011, 08:52 PM
  3. Hello! New Guy and a couple of questions..
    By Ryan07 in forum Chevy Trailblazer Forum (GMC Envoy)
    Replies: 6
    Last: 06-17-2010, 09:00 AM
  4. new here... couple questions
    By mx152 in forum General Chevy & GM Tech Questions
    Replies: 3
    Last: 07-26-2009, 11:01 PM
  5. I have a couple questions
    By BuckeyeBandit in forum Chevy Suburban Forum (GMC Yukon XL)
    Replies: 5
    Last: 06-24-2008, 04:21 PM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts