Don't worry about forged internals, rebuilt tranny, or PCM reflash. You don't need any of it. It's not incredibly hard to turbo a 2.4 engine it's just time consuming providing you build your own kit.
If you get a kit for a Z24 Cavalier, most of the pieces will fit. You may have to get new intercooler pipes fabbed and you'll definitely need a new downpipe. Try to get a kit with some type of fuel management included. Stay away from the Maximum Boost "kit"!
Best bet is to piece together your own kit. Do some research and like 2fst4u said, visit J-body.org and check out the boosted section, there's a ton of info to help you out there. On a stock engine you can run up to 10psi providing you have capable fuel management. There have been others who push more and been fine but I personally wouldn't go more than 10 without stronger internals.
If you ever have any other questions feel free to ask.
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