No you are probably hitting fuel cut. Toyota has a preset value (that can be fooled with an HKS "FCD" Fuel Cut Defencer) and thats what you are hitting(probably) it usually takes over 16 psi or more to activate this. It is a saftey Totota built into the fuel injection. I have a big t4 and it took 16+ psi to hit mine with a Lexus airflow meter and stock injectors. You should first buy a Wide Band O2 sensor. You will always own it and you cant possibly make an intelligent decision about tuning without it. What Im saying is everything you change to try to get a better tune WILL be a guess without a WB. It seems like a lot of money for someting that dosent make your car faster but you can not make safe tuning decisions without it.
Your dad is wrong about the fuel pump causing your problem. You need an FCD but you shouldnt get one until you have a WB installed first. Read
this when you thuroghly understand it then read this last paragraph it will make more sence.
I never installed 550's and the lexus AFM worked great with no fuel cut up to 16~17 psi. My Air fuel ratios (AFR's) were perfect and I was safe to go above 17 after a walbro fuel pump, and water/methanol injection. What im saying is you will be safe to go up above 10 psi with an FCD but only if you have a WB and KNOW what your AFR"s are. You will probably only be safe to 16 psi but dont do it until you KNOW your AFR's.
The FCD isnt the devil Reg makes it out to be as long as you know your AFR's. That article is kind of dated, if you notice he dosent mention "If you have a WB you can make edcuated decisions!!!" Go ahead and start a thread to ask more questions about this and we will not hyjack this guys thread.