I've got a '91 sierra with the 305 in it. I recently tuned it up, new cap, rotor, wires and plugs, not japanese parts either, Bocsh products. I'm havin a problem with my low end power. wen I hit the gas from a stand still at a light or somethign,it seems like the engine just bogs down. It takes a couple seconds for the engine to get enough momentum to rev right up. could my fuel pump be ready to die? or my fuel filter clogged? or my cat clogged? like my buddy has the same truck and can pull a brake stand or burnoutlike nobobies business, and its all stock. any suggestionsor fixeswould be appreciated, thanks!

 

Do the fuel filter for sure..I'd say thats it.

A pump is a possibility,but it should really run BAD...A clogged CAT could do it,but she would steadily get worse till it won't go 10

 

could an exhaust leak at the manifold flange where the y-pipe connects have anything to do with it?

 

An exhaust leak would certainly cause a decrease in power, but I don't think as much as you are describing. Like Argon stated, I would check the fuel filter.

 

I had a similar problem but also had a slight knocking from under the drivers door that progressively got worse. The CAT was replaced and everything is fine. 2003 GMC Sierra 5.3 Z71

 

Yeah, I'm replacing the entire exhaust system in june. gettin headers, duals all the way back, pair of high flow cats and a pair of cherry bombs. gonna get a new fuel filter in the next couple weeks. Would you guys recommend shorty headers or the full length long headers?

 

it's the same problem i got with mine, change your o2 sencor and tell me if thats it

 

theres a vaccum line comming from the back of your throttle body, it comes arround the passenger side of the engine and is pushed onto a sensor, it had a green 3 prong plug into it replace it thats your trouble

 

probably the filter but it could be the pump or even injectors or 02 sensor, if the air filter needs replacing that doesnt help either.