I have a 99 Suburban that I have ls swapped and it had a gen3 6.0 in it. It never fired up super fast, normally takes about 5-6 seconds to fire. Sometimes i have to turn the key off and let it prime again. I swapped out the motor for a 5.3 for an unrelated issue and it seems to have gotten worse. It really seems to me to be not getting enough fuel in the startup but didnt know if timing might help that as well. The motor is a 5.3 with a texas speed stage 2 truck cam. Also I am trying to figure out if the misfires I have on #2 and 7 are a concern or if that's normal.
Suburban 5.3 9-20 after smoothing.hpt9-20 drive.hpl