i have a 99 sse and i have done a couple things to it i have a k&n cold air intake 180 thurmostat ,throttle body spacer with out throttle body screen, msd coils and wires and cat back exaust. whats should i do next?

check this out

https://www.gmforum.com/t278662/

Your well on your way, Id suggest u finish opening your exhaust, maybe some headers or a Plog.

I would suggest putting the MAF screen back

X2....with the screen removed you are not gaining anything and may actually be hampering the air flow. The other obvious problem is the ingestion of debris that can damage the MAF.

i took it out becuase zzp said i would get a couple more horses if i had a 99 and up i could remove it without any negative affects
is that not true??
how much hp would i gain form headers ?

With adding headers and opening the exhaust, you don't really gain HP, you recover HP that was lost due to the restrictions. So, you can recover around 10 HP or so.

As far as the MAF screen gaining you HP....I would like to see the proof that removing the screen in a car without other mods increases HP. Check out the prices for a new MAF for your car...I think you'll want to put the screen back in to protect the MAF.

They make a lot of claims. That don't make it true. 4 hp is within the margin of error.

Something else about the maf screen removal. Our maf'* are designed and programming is put in place to read the air with the straightening screen in place. This keeps the air moving in a laminar way as it passes the sensor.

I tested the theory of additional HP by removing my screen. Holy crap did I get a ton of power. It was retarded how much power I felt. Upon restarting my car the second time I found a P0171 Lean Bank 1 code. This means that the maf was unable to correctly measure the amount of air going through the cylinders and by reading the exhaust the pcm was adding a lot of extra fuel to keep up with all the unaccounted for air.

In other words, my car was running extremely lean and could have been damaged. Lean will run an engine hot and fast. You can't do this very long without damaging things. Each car will obviously react differently, however most forums and veterans of the 3800 community will tell you it'* a bad idea to remove the screen.

do you have the stock throttle body or a newer style one? they were different from 97 to 99 the 99 suposivley is the first year you are able to run no screen without running lean and rough idle this is info i got from zzp in grand rapids
did yours idle rough ?