Loose of power at low revs

It may be worth looking at the timing belt tensioner pulley bolt to see if it hasn't worked loose, the belt may be about 3/4" of slack, which could cause the belt to slap against the inside of the cover at low rpms. It can also slowly shave away the backing of the belt. There could be about half a cup of timing belt dust/shavings collected in the bottom of the lower timing belt cover.

timing belt/chain slipped or low fuel pressure

Did you notice a change? I have a car like this and 1st gear is quick. There is not a lot of power.

First, check the condition of the following:

1) Spark plugs
2) Spark plug leads
3) Air filter
4) Fuel filter
5) Coils


6) [Assuming the first items are found in good working order] Idle control valve operation and cleanliness.

ignition module possibly or pick up coil

sound like fuel filter stopped up.if you have distributor type engine your idle speed could be too low and ignition timing off a little.

Hi, I recommend you take the exhaust pipes loose from the exhaust manifolds to see if your exhaust is clogged. Start the truck--it will be loud. See if it will rev with the exhaust pipes loose. If yes, take the truck to a muffler shop to figure out if your converters or the muffler is clogged.
If it isn't a clogged exhaust, it may be that your timing belt/chain has jumped. We can check that next if the exhaust is open. It's a little harder to do, and your problem sounds more like a clog to me. I'll be here to answer your questions either way you decide to go.

try changing all the spark plugs first,,,,they do like good plugs in them, and with a misfire its a dead sert its a plug!!!!

You may need a new thermostat, and you want to have your timing checked. If this has been a gradual progression then I would go with the timing. You may also have a failing water pump impellor.

Blocked gas filter is most noticeable at HIGH SPEEDS.

If it looses power at only 3500 or so rpm's, most likely culprit is the throttle position sensor also known as TPS.

Does ur engine burn oil? Could be low compression, but unlikely.
Could alsobe, but unlikely, the coil giving a weak spark.

Whats ur mileage and is it an automatic tranny or manual? Give more details please as to what ur car does, IE sputters, jerks, weird noises, engine revs high but car doesn't go faster, etc.