I parked my truck for 3 or 4 days,and when I came back and cranked it, it sounded like somebody put one hellacious cam in my truck. The exhaust sounded different and the RPM 's were goin haywire goin from 1000 to about 200, never died but couldn't come any closer, so I let it idle a bit, got in it andt ook off,,it was still idling bad and the throttle was pretty unresponsive, when I got it on open road i floored it, it didn't take off very well , but after about 1st gear it seamed fine. Cranked it and killed it a few times to make sure and it all was good, then this morning I get in (about a week later) and the exact thing happens. Help!

 

Sounds from what your saying, your leaving your truck sit for quite a while between runs.
Are you sure your battery is OK and fully charged and importantly, can accept a full charge?
Making short journeys with heater, lights, raido etc etc along with the large crank draw on initial startup, takes a while for the alternator to put back.
Especially if you have a cell crapping out on you in the battery.
These trucks are very battery voltage dependant and need a good steady battery voltage to run the PCM and other electronic.
I'd start checks there first.
Al.

 

The batteries good as far as I know, ill get it checked out

 

It could be that your tranny fluid is draining into the reservoir. The flat pan filter plugs directly into the tranny pump, and it may take a few minutes to get the system back to pressure. Try letting the truck idle for a few minutes after it has been sitting.

 

Hmmm... did you check the tranny fluid level? That could be it though I doubt it. Sounds like a fuel issue to me, how many miles are on the truck? Do you let it get down to E before filling every time? Could be your fuel pump going.

 

It did it to me again this morning, so I decided to be a little more thourough , cranked it , it imideatly started idling bad, exhaust doesn't sound the same, exhaust smells different ,kinda rich, I let the truck idle in my drive way for 20 min, with a few good revs, till it got warm, still idled bad, got in it and took it maybe about half a mile at WOT and my check engine light started flashing only at WOT came home killed it cranked up normal, trans fluid id good, gauges are perfect etc. My check engine light has been on for 2 years for EVAP codes, haven't had a problem with the truck in two years,short of replacing a starter

 

What's funny here is after reading your initial post I was going to ask if you had any codes - especially any regarding an evap leak.

Those CHECK ENGINE LIGHTS COME ON FOR A REASON!!!

Find and fix your evap leak...

 

You wanna help me narrow that down? Just pulled 3 codes, P0442(EVAP),P0456(EVAP), P0300(random misfire)

 

There is a map of the entire evap system in the FAQ section, pay close attention to hose ends and clamps, especially around the canister.

Also, don't discount a broken manifold bolt or two - common.

If you installed the comp260 and used the stock '03 valve springs I'd pull the covers and give those a good look also...

 

I think those evap codes are what I had. After crawling around under it looking at evap system, found a broken plastic cheap hose clamp and another missing. Put on hose clamps, cleared codes, all is well. But mine never ran rough. You may have a good size leak. Look for cracked hoses.