Cold Air Intake???
 

I have a 89 F-150 with 5.8L, is it a good idea or what are the benefits to installing a cold air intake? Thanks.

No benefits except it looks cool and makes noise.

x2. A proper tune is always better. The stock intakes on fuel injected vehicles are sufficient enough to outflow the throttle body.

I've always argued that they are an improvement. I've gotten better mpgs with all 3 vehicles I've had them on. Better sound inside. But the mpg gains on that old of a truck that probably gets 12 mpgs isn't going to even get probably .5 mpgs more. I gained 1 ish but already got 20+. I loved the more aggressive sound on all 3 tho. I would say in your situation, not worth it.

K&N Air Filter helps with non stock muffler, otherwise, stay stock! my 2 cents.

It very slightly changes exhaust tone. But inside the cab it sounds a lot more aggressive. Even with a 4.2 it sounded great. The 08 was a lot better than the 04 heritage in sound both exhaust and inside. The 08 had a 2.75 inch exhaust tho. I think the 04 was 2.5 or maybe even 2.25.