Is there any performance gains to be had from this?

Also, is the L27 Intake one piece or two piece? Its about time I change the LIM gaskets anyway, so I figured why not pick up a little power if possible.

I've got a '89 3800 LN3 with 2 1/4" exhaust with a cat delete, $15 cone air filter clamped the to the throttle body, and a free flowing muffler.

I believe some doors can be opened with this. I am not too sure about some of these things, but it gives you an idea where to start looking. The intake manifold on the L27 is 2 peices, the upper <metal until 93, then plastic composite there on> and the lower. I don't believe it is a direct bolt on, I think the heads would need to be swapped over. This leads to another thing. If you swap to 94-95 L27 heads, you can easily swap upgraded rockers.

I could upgrade rockers and get a little more lift I suppose.

Any idea where I can find the list of RPO codes to figure out what my gear ratio is?

This car does not run too bad to begin with. The original owner was my grandma, and it was fairly well taken care of. Its definetly a LN3, but its got what are essentially steel headers on it that was supposed to come with some earlier version of the motor.

With a L27 Intake Swap, CAI, Cat Delete, and 2 1/4" free flowing exhaust what could I expect to run in the 1/4 mile depending on my gearing?

You can enter your vin here http://www.compnine.com/vid.php ...But i warn you you should becareful..having a 4t40 trans they are not the strongest

For some reason my Vin never runs through Compnine. I use it all the time, I've also got a First Generation *-10 fetish.

Take a look here.
https://www.gmforum.com/specifications-general-information-132/rpo-codes-279296/

Is there anywhere on these cars where the RPO sheet is printed or stamped? On *-10'* and Camaros there inside the glovebox, but there isn't one inside of mine in the Delta?

Any ideas?

RPO sheet should be on the spare tire cover. You will want to confirm the VIN to ensure it wasn't swapped.

Will do. I'm crossing my fingers for a 3.something ratio.

Given the nature of the car, I doubt it however. Our '90 SSE had the GX3 (3.33) and it feels like my PA with the 2.84 has a lot more mid range punch. Many feel that the ideal gear ratio for the Series 1 and LN3 is the 2.93. The 3.33 likes to keep rpms past the power band, and the 2.84 is a little doggy at the extremes of the gears <low and high>.