when i bought my car the previous owner dropped in a 350 in place of the origional 305. he left the 305 computer in and i think that is why its running like s%&t. idk anything about this kinda stuff so any help on how to do this would be appretiated. thanks

 

its not the size of the engine, although it could be. it is probably the intake. if he went from tbi to tpi then there is a problem as nothing is the same in the computer system.
it could also be, if it was tpi to tpi that the injectors are the wrong size, or that the prom has not be changed to take into consideration different injectors, engine size, etc.
you have an 86 so you probably have a maf tpi if you have tpi. there is a change in knock sensors too.
it could be the wrong size fuel pump.
it could be anything.
you need to provide a lot more information.
what you have given us is like a man walking into a doctor and telling him that he does not feel well and having the doctor immediately tell him what is wrong. the doc needs a lot more information and so do we.
good luck.
now the real fun starts.

 

The computer is the same, the memcal is what is different.

It needs to be programed for the 350 (tuning).