Yeah, those Aldi Poppers seem to be turbo powered alright.
Havent had a chance to try the Purosa yet but I have roasted other varieties from PNG, most recently the Sigri. In general, I have found the PNG beans to be pretty straight forward to roast and able to be taken deep into 2nd Crack while still retaining a significant proportion of the beans flavour profile... not into charcoal territory though ;).
Id say the problem you have experienced is mainly due to the Aldi Popper itself more than anything to do with the bean. If you can reduce the output of the main heating element that will no doubt help quite a bit. Alternatively, you could ask a friendly local electrician to mod your Aldi by splitting the power supplies to the Heating Elements and the Blower Fan, then fitting a Solid State Fan Speed Controller (can be had from most Bunnings and similar stores quite cheaply) to the Blower Fans supply. This will give you the ability to increase the Blower Fans Output and tailor your Roast Profiles to a much greater degree and probably increase your roast batch size into the bargain. Depending on the electrical circuit configuration of the Aldi Popper, your sparky might have to obtain a small 240V/30V Transformer to supply the Fan. These are pretty cheap items too and wont add much to the expense. A really valuable tool to have on hand for a wide range of uses by the coffee geek, is the Digital Temperature Probe... usually an inexpensive Digital Multimeter that comes with its own K Type Thermocouple Probe. This little gadget will allow you to set up your roaster so that it roasts as near to perfection as you can get with a popper and that is definitely worth doing.
For most of my roasts, I try to exceed a lower time limit of 9-10 minutes and generally not longer than 13-14 minutes for batches of between 100-120 grams. If you could try and stretch your roast times out to at least 8 minutes or so, you will definitely be able to taste the difference in the cup. Combined with adjusting the Roast Temperature or the Fan Output, you could try reducing your batch size by 5 grams at a time and see if this provides you with a more realistic roast time.
Youll be there in no time Steve and then enjoy the wonderful aroma and flavour of home-roasted top quality coffee... nothing better ;D