ok here is what i got. i used to have a lo3 tbi, swapped it out to a crate motor 350 longblock, i put on my 305 tbi with 305 injectors and the stock 305 computer. i would think that would make it lean since it is feeding 45 more cubes with the same amount of fuel. also i am getting 11 mpg, hence the reason why i think it is rich, had 20 with the 305. finally, once in awhile it will backfire through the intake, won't kill the engine but it is very close to killing it. timing is set at 8* btdc. also have a .460 lift cam in it. sorry this is so long just wanted to put as much info in here as i could. anyone have any ideas????

 

Need to know the lift @.050 and LSA on the cam. Are you using the distributor from the LO3? Is the SES light off? It sounds like it's in limp-home-mode or the program in the ECM is hating the cam. The air/fuel requirements of the 350 shouldn't come into play until 3/4 throttle and above.

 

duration at .05 is 218* on both sides advertised duration is 284*, lsa is 110*
yes i am using the 305 distributor, i am not getting any codes at all, except egr valve after long trips ( took it off)