i own a 2005 srt-4 wit a few mods done to it
mods: 3 inch downpipe,3 inch o2 housing, mopar exhuast. cold air intake. stage 2 wastegate, boost controller, agp motor mounts, agp tranny mount, boost controller at 20 psi

 

Forget a chip not sure they make one, get a stage kit, alot better and more hp

 

if you dont have a at least a stage 1 chip then 20 psi is sure to be pulling timing and robbing you of power. i would go for a stage 1 chip if you can. either that or get a wideband and a map clamp to trick the computer into thinking its getting less boost.

 

I agree with you needing to get a wide band gauge, but turn your boost down, the stock turbo it not good for that high, if you want 20 psi then get a stage 3 kit, thats too much boost for the stock turbo, set the wg to 12 psi and your bc to 16 maybe 17psi, the stock fuel system can handle 20 psi either, its only good for 18.