Stalls when taking foot of gas pedal

So I brought a cheap (truck listed above with a g6 engine) that had been left sitting for a year after having a lot work done to it like; panel and paint glove box, differential rebuild, new exhaust, wheel bearings, ball joints, injectors and radiator etc, etc. It didn't start one morning and owner just gave up an left it. I have replaced fuel filter, starter, exhaust manifold gasket, battery, but now after doing approximately 1,000 kms in it it is now stalling when I take foot of gas while driving or trying to park at shops and sometimes when parked. If you rev it then drop throttle quickly it shuts off too, but only does this once at full running temperature. When cold it never stalls. What's my next step guys?