1994 Dakota run's like as* plz help me out 3.9 magnum plz help asap (busing sucks)

[starpuss]

-right now the tuck has a new plug ands spark plugs
-right how it will start up and run like as* and it will some time back fire when u ''puntch it and let go of the gas;;
each of the cylnder have 175-182 psi
when i got the tuck (3) week a go it started up after 2 min of cranking (but i had to give it gas a lot then it stated then shut down so after trying it for 5 min it ran but when i let go of the gas'' this is when it was runing for 10+ min it would not idle right

and right now i think my ''cat'' is pulged (from look ing at other post's)

after leting it sit for 5 day
i when to start it and / nuting not even a litte bit of nose till i ''gave it a cap full off gas down the intake'' then i ran for 2-5 sec but it has i think it was 40psi of gas but maybe one of my injector are pluged?

and it has a hissing sound under the hood . when not in cab. Any info will help alot
like a '''''''big ''''' vacum leeekkkk
cat plug ????????.

it would help me a lot if u can post some info on what it may need plz and thx

(sry a lot for my bad english)
and o ya it is a 3.9 magnum

[Jon Teeter]

If you have fuel and good spark it may be a vacuum or the EGR vavle.You can take the EGR valve off and clean it. If there is build up in there that will cause the engine to idle rough and may not run good unless your giving it gas.