A good piggyback, if you want to go that route, is a PP SMT-6. My buddy, down in Florida, is an authorized distributor..
For a little info on the SMT6:
The SMT6 is designed to allow you to tune just about any engine, the SMT7 will tune computers with odd crank/cam configurations that the SMT6 can not. Signals are modified on maps by using windows software. Installation and tuning is simple and once installed the engine can be retuned by anyone with a laptop and the tuning software. An average installation consists of connecting 5 wires (sample wiring below) to the vehicles original wiring loom, changing the settings of the unit in the setup section of the tuning software and you are ready to retune the car. It has been found that an experienced installer can install an SMT unit within 30 minutes.
A full list of the features and benefits of the units are listed on a chart below, here with an explanation of some of the latest ones:
Things that put the SMT product above other piggyback units..
There are two modes of lambda tuning, the first is a linear mode which tunes according to the voltage of the sensor. The second is non-linear which allows you to tune according to a lambda value. Both tuning modes are selectable via the setup screen.
The older SMT5 had an output that was enabled according to a RPM set point. This was mainly used with cam switching applications. With the SMT6, it is possible to set this output to airflow, temperature and analog deflection points as well.
The extra injector driver can also be used for proportional nitrous injection, something its predecessor could not do.The SMT6 has an input for airflow sensors and temperature sensors, each have a separate map that can be used to manipulate the fuel, extra injector and ignition signals.
BENEFITS OF THE SMT6
All piggy-back units are reliant on the existing ECU to provide the fuel and ignition to the engine. For this reason they are bound by the limitations of the existing ECU. Fuel is typically modified by changing the load sensor or lambda sensor signal. Ignition is done by delaying or advancing the crank angle sensors signal. The piggy-back unit tricks the ECU into thinking that it is running under different conditions thereby allowing for a different output.
The SMT6, like its predecessor, has the ability to drive an extra injector which will allow more fuel to be added into the engine typically for turbo applications.
FEATURES
Throttle Sensor learning feature -Fits to any throttle position
RPM Calibration - To suite your installation
High RPM range - Racing?
Fuel map with 128 sites - Smooth Programming
Ignition Map with 128 sites - Fine Ignition resolution
Injection Map with 128 sites - For extra injector output
0 - 10 volt analogue range - Allows tuning of all models
6 Amp injector driver - Handles up to 6 x 16 ohm injectors
Various ignition outputs - For the most stringent applications
Selectable Trigger points - To suit
Programmable Cylinders - It works on any amount of cylinders!
Selectable polarity - To Suite
Can handle interlaced signal - For 4 cylinders ignition output tuning
Balanced Inputs - Inverted Outputs
Missing Tooth Signal - For up to 2 teeth advance/retard
Ignition output limit Limits - max. advance and retard
Fuel High low limit - Prevents overdriving the ECU
Small Size - Fits Anywhere
Map Switchable - While you drive
All Inputs Protected - No mishaps!
Crystal Controlled - For Stability
Encapsulated - For Moisture and Dust
Easy Tuning Software - DOS or WINDOWS
10 MIPS computing - To facilitate quick engine response
Signal Conditioning - To prevent miss trigger
Engine profiles (over 650 wiring diagrams) - Easy set up
Lambda Signal Tuning - Modification of Lambda Senor Readings
Proportional Nitrous Control - using extra injector output
Adjust Dwell Time - For very basic standalone applications
Rpm / Airflow / Analogue Defection / Temp Switch Point - For cam switch and similar applications
He sells the SMT6i for $390, and the SMT6i + 2.5bar Map sensor (22psi boost) for $450. A real nice advantage to these PB units is that they are very small... like 3/4" thick, 4"wide, 4" tall...
I've used these on a couple of cars, and they are easy to set up, tunes, etc.. Even have a "learn" mode.. This was especially useful when I was converting metered-air sensored cars (Merkur, BMW) to speed density (MAP)...
Hope this helps some...
With the availablilty of dual switchable maps, you can create an aggressive map for power, and an economical table, or "emissions" table
And they do have smog legal turbos, Right?