No. It's not even close to 300 horse NA.
Stop it.
Local only made 212 WHP/220WTQ with Ported Heads and a GT2 cam with an HV3 and full 3" exhaust on a 3800 SE.
You're also not gaining ANY power from deleting the cat or EGR, unless it's currently clogged. Meth kit isn't needed on an N/A 3800. Just convert it to corn if you want anything better. 91 octane is plenty. I ran ignorant amounts of timing and a lean AFR in my silver with Efree93. It was running with GTP's with ease. Mods were in sig.