?? about the sonnax line pressure booster

These LP boosters "adjust" the sensor reading, making it appear that line pressure is lower than it really is, so the controller will crank up the pressure (until it reads high enough). I don't think a small "adjustment" will hurt much, but I'm not sure it will help either. The controller learns the minimum line pressure needed to avoid clutch slippage. And that's not a single value - the LP is adjusted continuously depending on temperature, throttle opening, gear, etc. So let's say the minimum LP (for a certain set of conditions) is really 50 psi, but your LP booster is faking the sensor by 10 psi. The controller will "learn" the min line pressure to 60 psi and set it there, but in reality you'll still be at 50 psi. So you get no real benefit. There are some times (like during shifts) when we use a fixed LP value, so you would get higher LP at those times, but then the shift parameters (solenoid duty cycles, etc.) are also learned, so again you'll probably just learn those parameters to different values so you get the same shift performance as before. One area that might cause an issue is the fact that we set a fault if the LP sensor reading is too high (greater than 4.75 V I think). At max line pressure in Reverse (250 psi I think) the sensor reading is just below this threshold. So if your booster cranks the voltage up above 4.75 V, you could blow a fault, which would put you into open-loop line pressure control (where it ignores the sensor altogether). This would NOT light the MIL, by the way.

Bottom line: I don't think an LP "booster" will actually do much for you. You may get firmer shifts initially, but then the TCM will re-learn the shift adaptives (to give you smooth shifts with your new, higher line pressure) and you'll be right back where you started. So I wouldn't spend my money on one of these "boosters."