94 Camaros and Birds came with a 3.4L V6 option, how did you get to 3.5L, swap in a 3500 short block? I'm pretty sure I was the first to do something similar years ago prior to the 3500 front wheel drive motors being manufactured. Provide some real details and pictures of your swap so that some informed opinions can be given. I bet your turbo lag has all to do with old habits being applied to new technology, a ridiculously low compression ratio. Not even factory turbo cars come with compression ratios below 10:1 anymore.
I once owned a Firebird, and two IROC-Zs with the tuned port motor and learned a lot about the cars. I've also done a lot of traditional turbo setups and figured out that higher compression is the way around turbo lag instead of small turbine housings that choke the top end.