The HPFP with the GH turbos on e30 with make more power than the stock motor can handle. BUT you can use meth just for cooling and cleaning at the same time. You don't need a lot just go until you almost bottom out your short term fuel trims.
You can buy just the sct device, 3 bar and a tune if you don't want to do plugs and t stat.
https://ghtuning.com/products/2010-2019-sho-flex-explorer-sport-sct-x4-power-pack-package?srsltid=AfmBOooFJ8r6rJ4v22oVrQZcvfDsnQw3x9zaOkyRZ93s94O5M1INUpFb
This.
The factory tune is less than the turbos are capable of this why the factory only used a 2 bar. The turbos can not put out more than the motor can take so the 3 bar let's you push the boost to the max the turbos and fuel will take. Gear head has what you would call plug and play best bang...
The factory pipe bend are restrictive. BUT. There are a few modes you need to do to take advantage of before you will see any gains out of the DPs.
1, Get a tune from AJP or GH and add a 3 bar map to the top of the intake. you will need to tell the tune about the 3 bar. And best to do colder...