Tuning off of a base map

I am new to tuning, I’ve been watching the ECU tuning fundamentals videos to try and learn more but I usually understand things better when I hear from people and their experiences. I’m currently tuning off of an ECU masters emu black base map for a 1999 Lexus gs300. I know the base map doesn’t account for the engine being boosted and having a whole new fuel system, intercooler and a newly built engine with a different compression. I’ve done all the basics of getting the engine started, checking timing, compression tests, oil pressure. It’s idling good, but the Lambda shows 1.01 for about 10 seconds at startup then falls down to .70-.75. I lowered the values on the VE table in the Idle range down by about 15%-20% and got the Lamda to match the target of .98 however if I rev even a little bit, the lamda value drops then shoots up to 1.3 to 1.4. I know that would be from the engine not receiving enough fuel compared to air. Again I haven’t tuned before and I’m using any knowledge I’ve gained from my courses, where else should I start? Something’s to note is I am using the turbo and intercooler kit from CX racing for my car with the thick tube turbo mani. Borg Warner S366 A.R .88 66mm inducer turbo with a custom exhaust system from the downpipe all the way back to the tail pipes. I still have my MAF plugged in and installed into the intercooler piping as well as using the MAP sensor that’s built into the EMU black. The EMU black is running PNP kit to the stock ECU.

You need to adjust the VE table to match what your engine wants. The fastest and best way is to use a load-bearing chassis dyno. There you can hold the Engine RPM steady, and increase the load to hit all the cells. If you're just working in the garage, start with just tuning the cells you can reach by slowly opening the throttle. If it goes lean as the next engine speed cell is reached, then increase the VE in that new cell (or two cells if you are between two load points. This should give you some trends you can use as the loads increase.

Remember to only tune the VE cells when the engine is at operating condition. Adjust the operation when it's cold with the the coolant compensation/trim.

Good Luck!