Getting a 4age 20v blacktop to run right can be a real mission. I finally had a break through today. What I was doing wrong was to try to correct the air/fuel mixture with a Apexi Safc2. This device only tricks the ecu by sending back a modified map sensor signal. What I didn't realised was the standard 4age blacktop ecu mainly chooses the air/fuel ratio based on the TPS throttle position sensor. This came to light when I took my wife for a slow drive and I left the tps screws semi loose. On the way to a farm out the back we did a lot of over run down the hills and I could hear the engine burbling rich on deceleration. I stopped and turned the tps clockwise to lean it out. Straight away the mixture changed. No more rich overrun. I then set my adjustable fuel pressure regulator at 51 psi and set the Apexi Safc2 at zero modification levels. Next day I set out to only adjust the fuel mixture by adjusting fuel pressure and the throttle position sensor. Success. Best it has ever run. I also found disconnecting the vvt helped heaps and took a huge surge and hesitation out of the full throttle pulls. Maybe my vvt pully is not so healthy. I also disconnected the o2 sensor. If I was trying to summarize what I am saying it is this. 4age blacktop ecu's rely heavily on the tps sensor for their main decision making input. Adjusting map signals helps very little. Finally if you own a 4age20v blacktop and can't afford a link, haltech or motec ecu you can get good results with a fuel pressure regulator a disconnected o2 and a adjusted tps.