1997 astro misses at 50-60 mph with steady pedal pressure. when under acceleration runs fine. Also misses while passing through lower gears when starting from a stop.

I really need to know what size engine you have in your Beretta as well as how many gears are on the shifter as in low one low two Drive with a circle around it or one two three drive with a circle around it sounds to me like a torque converter pressure switch when vehicle is shifting into overdrive switch is not operating correctly releasing pressure from torque converter causing vehicle not to have enough counterweight for transmission until vehicle slows down and then will operate again shifting through gears until the Overdrive goes to kick in send more info

'Passing gear' is a term that means the transmission is down-shifted to a lower gear (e.g., from 5th gear to 4th gear) for improved acceleration to pass another vehicle. There is no physical component called a passing gear in the transmission.
To engage the 'passing gear' with an automatic transmission should require nothing more than pressing the accelerator pedal down firmly. The transmission should downshift automatically to the next lower gear (sometimes it will downshift two gear ratios, depending on your speed and how far you depress the accelerator pedal).

Odds are you can't feel it in the lower gears, replace plugs, check wires to start, then check coils

1. The testing has to start with the vehicle under 122 degrees F. Start the engine and idle for 2.5 minutes in Drive (auto) Neutral (MAN) A/C and rear defogger ON.

2. A/C OFF, accelerate to 55 MPH at 1/2 throttle and then 3 minutes of steady state cruise at 55 MPH.

3. Clutch engaged (MAN) no braking decelerate to 20 MPH.

4. Accelerate to 55-60 MPH at 3/4 throttle and 5 minutes of steady state cruise at 55-60 MPH.

5. Decelerate, no braking to end the drive cycle.

In some cases the Powertrain Control Module (PCM) will go into a logic lock not letting the readiness monitors run. Removing the battery cables and touching the two together will normally take care of the logic lock condition.

sounds like the lambda sensor or crank sensor. does it work fine from cold?

At a steady 65 mph, the torque converter clutch (TCC) is engaged. When you accelerate, the ECU disengages the TCC to gain extra torque for acceleration and then re-engages TCC when speed is steady. Its kind of like having an extra gear.

Sounds like 2nd gear in the transmission is slipping. Cars usually shift at 15-20 mph from first to 2nd. First check the trans fluid.

A variance of 20 PSI indicates a problem.

the best way to reset it is with a scan tool.
disconnecting the battery for one minute will also remove the code.BUT
if your smog test uses an OBD scan as part of the process,then there will be a problem,because the monitors will not have been set,as they are reset if the battery is disconnected..
most tests allow only one monitor missing,and not the catalyst .
A drive cycle will have to be done to set the monitors.
Typically cold start coolant temp less than 50F,idle for 2 minutes no air condition, accelerate at half throttle to 50mph then drive 3 minutes with a/c on at 50mph steady.decelerate to 10mph without using brakes..Accelerate to 60mph and drive for 5 minutes at steady speed without a/c
deccelerate without braking and drive for 1 minute at 40mph.
stop the car ,use braking.
Shut off the car and add 4 gallons of gas.do not shut off the car for more than 5 minutes.
drive in 3rd gear or overdrive off with rpm 3000 for 1 minute.
decelerate to 10mph.without braking
accelerate to 40 mph in 4th gear.,or overdrive on
decelerate without braking to 10mph.
test complete.
this will set the o2 sensor heater ,o2 sensor,catalyst,evap purge.and the other monitors.

From minor problem to major problem. Try to replace your spark plug wires, rotor cap and the spark plugs, also it can be the injectors, plus if possible, try to replace the fuel filter which is located low under your EFI unit. If problem not solved, then it will probably be your A/T trans.