Just hooked up new pressure asist tank & bowl,turned on water to it,and it want flush.what i mean about want flush, is it will flush but water does'nt go down,as if it's not staying open long enough.

You probably have one of the newer Cimarron-series toilets that feature what Kohler calls "AquaPiston" technology. These gadgets use the water pressure in your supply lines to pressurize a charge of flush water in the tank, causing the flush water to rush into the bowl at high pressure and velocity. Many Cimarron-series toilets use only 1.28 gpf (gallons per flush), compared to the current industry standard of 1.6 gpf for conventional gravity-flush units. Reducing the gpf rating by 20% requires pressurizing the water in the tank, and the release of pressurized water makes a lot of noise. I'm afraid your toilet will always be noisier than what you may be used to.

Pressure assisted toilets have a stainless steel tank that refills under lid,if your refilling bowl it only needs to fill trap for smell,the pressure assist does the rest,thats part of the water saving of the toilet,you don't have a lot of water in the bowl

Its simple. Check to see if you installed toliet right by removing top of tank and holding handle all the way down. Did it flush from all rim holes? If not, then u will need to get a garden hose with a sprayer to increase pressure and shot high volocity water at rim holes to unblock it. Remember the very front on newer blows do not have holes its a pee shield. Also try doing these other things adjust screw inside tank to make sure the bowl has enough water in it to do a good job. Check the rubber tube going into the hollow pipe and make sure it is going fully inside the plastic pipe that is sticking out of the top of the water in the tank. Also you need to have enough water in tank to allow it to flush good. To increase tank water levels then just unscrew the big plastic ball (or just bend wire to allow more water or bend to allow less water) at top of water in tank. Also increase (max) water pressure at wall to allow it to work at its best. If you have hard water it can cause problems but you say it happened even new, so, you do not have to go in that direction.

Wiith all due respect, the Drake toilet is not a regular toilet and doesn't sound the same as a regular toilet when you flush it. It is in the design that allows it use only 1.5 gpf instead of 3.5 gpf. A rather unique thing is that while it is scientifically calibrated to release 1.5 gpf, it does not empty the tank of approximately 1 gallon of water. Therefore if one feels the need for a little extra umph, simply hold down the flush lever when you flush until the tank is emptied.

As long as there is no water leaking from the tank to bowl connection, you are OK. You would know if it was leaking here, because you would have water dripping out onto the floor.

Verify that the water level in your tank is below the top of your new flush valve's overflow tube. If the water level comes to the top, it will overflow into the toilet bowl. This can be easily fixed with an adjustment to the fill valve.

If the water is not overflowing into this tube, then the only way you can lose water is through the flapper. You said you changed the flush valve, which would have come with a new flapper attached to it, but maybe buy a new flapper and see what happens???

Most likely, you do not have a good seal on the flapper valve at the bottom of the tank. To confirm, try this:
Turn off water and flush toilet. Then lift up the flapper valve and put a light coating of vaseline on the mating surface where it contacts the toilet tank when closed.
Turn water back on and see if it continues misbehaving. If that fixes it, it was a bad seal. Usually that is all it takes.

is the black thing between the the tank and the bowl?
if so, go to any of the home center or plumping store for the seal.
shunt off the water and unbolt the 3 bolts that holds the tank to the bowl from the buttom. you may need a flat screw driver to help hold the bolts. pull up the tank slowly, and lay it on the side, replace the seal, reseat the tank on to the bowl and tighten the bolts. make sure all bolts are equal pressure and the tank is level.

increase the tank water level half inch at a time till you have the back flush pressure.
seems like the water in the bowl is too low to create any wirlpool.