The 2007 F1 champion was uncomfortable with aspects of the Ferrari F14 T's characteristics throughout testing and the season-opening Australian GP.
But Raikkonen was second fastest in both Friday practice sessions at Sepang.
Although he continued to play down his prospects, he acknowledged that the timesheets reflected a genuine improvement since Australia.
Friday practice 1 report
Friday practice 2 report
"This was definitely a positive day and I had a better feeling compared to Friday in Melbourne," he said.
"I was more comfortable with the F14 T today.
"Even if we had no problems whatsoever, we know there's still a long way to go and a lot to do."
Both Ferraris showed promise on longer runs in particular, with Fernando Alonso fifth in practice two.
Alonso refused to make any judgements about the form Ferrari had appeared to demonstrate.
"We are on a learning curve, which is not unusual for the start of a championship and, to find out how competitive we are, as usual we will have to wait until Saturday and Sunday," he said.
"Usually, Friday is a very confusing day, because everyone is working on their own programmes, but this year it's even more the case because of all the new elements.
"Everything went well, with no reliability problems and we managed to do a fair number of laps."
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