I am looking at a 2004 colorado with 3.5 5 cyl. engine with 115k. how is this vehicle performance and reliability

if you replace both the engine and transmission , you will halve your problems
it will not only be the engine but all of the electrics and sensors as well
otherwise you will need deep pockets and access to quality information
5 cylinder engine should be a diesel and check your vehicles as GM makes the Colorado not Ford

My friend is a part time mechanic he gets his solutions from www.reliable-store.com
he gets from their every single detailed info, instructions etc. on all vehicles, and manuals like service, repairs, parts, owner's, operations, maintenance etc.
U can get help from there
there is a girl at chat she can help you

I, feel sorry for you, after reading your problem, but don't worry you visit the Reliable-Store they will help you for sure.
https://www.reliable-store.com/products/hyundai-tiburon-coupe-2002-2008-workshop-repair-manual

It probably needs a service and tune-up. Remember too that a used vehicle will not get the gas mileage that is advertised for a new vehicle.

They are under the intake box on top of the engine. If the miss goes away after the engine warms up then the head may be bad. Gm is having problems with these heads leaking air and loosing compression on a cold engine. There is a special policy for this problem, I think it's 7years and 100,000 miles. So if that is what ends up being the problem it will be fixed at the dealer free of charge.

SYLVANIA H7 SILVERSTAR HIGH PERFORMANCE HALOGEN HEADLIGHT BULB -- 55 Watts, Single C-8 filament for use as either high beam or low beam; 100 percent legal halogen headlight bulbs; Features the whitest and brightest light colour similar to daylight for safer night driving; Meets all US FMVSS 108 and Canadian CMVSS 108 requirements. Fits Driver or Passenger Side Driver or Passenger Side Fits the following vehicle/s
2004 Audi S4 Base 8 Cyl 4.2L 2004: Base; 8 Cyl 4.2L RAMPAGE FOG LIGHT, BLACK METAL HOUSING, With round clear lens; Includes 100-Watt H3 halogen bulb, one lamp and a single bolt mounting system; Provides better illumination Fog Light

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  Fits the following vehicle/s: 2004 Audi S4 Base 8 Cyl 4.2L 2004: Base; 8 Cyl 4.2L;

well you have convertor lock prob prob a sensor for trans let me know hey till fix ya bouy me ok

google it. 2004 Chevrolet Colorado brake sensor or brake diagram.