will lack of back pressure for example running a stock d series open header cause it to bog down or even cut out when you hit the gas then let off and before you bash the reason its open header is cause we just swapped the motor and fired it up to make sure everything ran but when we hit the gas it revs up then when you let off it eathier bogs really low or even compleatly shuts off and you cant just re start it you need to give it some gas when starting it if back pressure isnt the issue can someone point me in the right direction before we spend a bunch of money on things we do not need. i was thinking also it might be a fuel shortage bad fuel filter or fuel sock on the fuel pump we checked the vacume lines but havent got a chance to spray them with carb cleaner it got dark and had to call it a night. it also has brand new plugs and also there is a check engine light because the O2 sensor is not connected

 

the open header wouldn't cause that to happen, it sounds more like you have a vacuum leak somewhere. I would check your lines again and make sure there all going to where they need to be and also check your IM gasket aswell as the TB gasket.

 

Why is the o2 sensor not connected? OBD1 or OBD2? Correct ECU? I don't think having a lack of some back pressure would cause this, I would agree with checking vacuum as well.

 

the o2 sensor isnt connected cause we cannot get the factory one out of the stock header an we are waiting for a new header to come in i will make sure i re check the vacuum lines not many were disconnected so it shouldent be hard to find if one is wrong but i will spray them all with the carb cleaner to check for leaks. also we found that the water pump has a bad gasket could that cause ne problems ?