I have a similar setup in a Fiero. (Yeah. I'm "one of those".)
A '91 4.9 with a '91 Allante intake system.
I've combined the Allante and Deville programs into what should be a workable tune, but I can't get a part throttle ping (spark rattle) to go away. (Other than that, it goes like hell. )
I'm not really asking for a solution in this thread. I've got posts all over the web, with specifics. Just wondering if anyone has swapped in a 4.9, and whether you've had similar issues.