The Chairboys stunned Fratton Park by taking the lead in just 13 seconds through Joel Grant's curler. Dean Morgan doubled Wycombe's advantage after nine minutes before Pompey striker Izale McLeod pulled one back.
But Morgan finished the job when he headed home the rebound from his own saved penalty after 55 minutes. Ainsworth believes there is more to come from his team, but admits he may need a day off to let victory over one of npower League One's big guns sink in.
He said: "I can't thank the players enough - they were awesome. The way they went out there and defended beggars belief. Some of the last-ditch defending was fantastic.
"I might have a down day on Wednesday. I'll just have to chill out and maybe have a lie-in - I'm really, really pleased. I don't think I'll be able to sleep in all honesty. It was a solid, solid performance, but there is still work to do, definitely still work to do.
"I want to get better and there are still little bits we can get better at. But you've got to enjoy coming to a team a league above and getting a result like that."