So whose using a rising-rate fuel pump regulator?, Not turbos; or using a cold start valve as a 5th injector? Options

[computers4kids]

Who has played with a rising-rate regulator or adding a switch to a cold start valve to be used as a 5th injector to get a little extra pony power?
Here's one...
MicroDynamics RisingRate Regulators are designed for use with all types of fuel injection systems. Added to standard systems they increase the mixture range for high performance or provide "boost or load enrichment" on both turbo and naturally aspirated engines. Rising-Rate will also give more fuel at the top end without going over-rich lower down the rev/power range.

A MicroDynamics RisingRate Regulator is often the only form of fuel enrichment required for many retrofit turbo conversions and is usually the easiest way to obtain increased fuelling on production injected race vehicles.

Here's one by Bell Engineering $179

Here is an interesting article how to make your own rising-rate pressure regulator from a stock 914 regulator