I've had an aftermarket downpipe for over 10 years without a tune.

[MSMS3]

You might want to look at my mods. You need a hpfp upgrade and a tune.

Believe it or not, on the stock K04, the often derided Hypertech tuner maxes out the K04 or pretty close to it with safe AFRs and controlled boost up to 18 psi with taper to a safe 14-15 psi while maintaining aggressive timing advance. And, yes, that is with a catless 3" downpipe and racepipe and an aftermarket CAI or SRI, if on their list of intakes for their MAF calibration tables.

With your mods it will likely get you a safe 300 whp once you upgrade the fuel pump.

If you can pick up a used Hypertech Max Energy tuner, that may be your best option and will get you 300 whp on pump 93 octane. New is about $400. If buying used, it must be unmarried from the ECU it was programmed to. Otherwise, it is a brick. Same with other tuners like Cobb AP, if bought used.

It will NOT work properly, however, if you use a different turbo, a larger diameter MAF housing or if you try to use ethanol or other fuel than 91-93 octane pump gas.

Either the plug-and-play Hypertech programmer,mor get a Versatune or Cobb AP tune compatible with your mods. The AP off the shelf maps are not very good.