98 power problems HELP!

My 98 sierra 1500, z71 seems to have lost its jam. When bought it i could stomp on it and roast the piss out of my tires and tow anything. Now, its impossible to spin the tires on pavement, even brake stands are impossible, towing the cattle trailer is a chore as well. Wat could my problem be? suggestions have been plugged convertors (which is lots of $$) or plugged injectors. Any ideas on easy checks for these 2 problems or suggestions on wat else it could be? any help would be greatly appreciated. any ideas to get more power without major/pricey mods would be great!

Mileage? When was the last tune-up done? What is the fuel pressure at?

Is the Check Engine Light on?

//2000CAYukon

recent oil and filter change, 02 sensor replaced, intake manifold gasket replaced, egr valve was replaced, engine light is not on. 200,000 kilometers or for u americans 120,000 miles. How do i check fuel pressure?

There is a test port on the fuel rail where you can hook up a fuel pressure gauge.

If the fuel filter has not been replaced for a while, I would replace it.

Engine running at idle, pressure should be 60 PSI.

//2000CAYukon

where is the fuel filter located on these things? underneath?

Inside the frame rail under the drivers side door.

//2000CAYukon

OK, the fuel filter did not help... any other suggestions?

Were you able to test the fuel pressure? Also check it after you turn off the key to see if it drops fast. It should hold pressure and drop one PSI every minute or so. If it drops fast (60 -> 30 in a minute), then your fuel pressure regulator is causing you to run rich (and hurting mileage and performance).

The EGR could still be your problem. EGR should function only we warm and at part throttle conditions. They do wear out.

Test the fuel pressure first and go from there.

//2000CAYukon