Gorbachev Offered Riga Line to Poland & 'Kalingrad Oblast' to Germany in 1990

'Riga Line' the pre-WW2 Polish eastern border with the U.S.S.R.
mutually agreed upon March 18, 1921;
plus 'Kalingrad Oblast' Sold to Germany for 48 Billion DM

Found this on a facebook page

In 1989, Mikhail Gorbachev suggested meeting in Moscow G-Dragon, the return of the Eastern Lands in two versions.

First: the return of Vilnius, Lviv and Kremenets;
 
The second arrondissement of Grodno from the wilderness Belovezhskaya Pushcha and the former province. The Lviv Centre for petroleum. The reason for this proposal was the cancellation of the jałtańskich agreements and mutual waiver of claims for compensation.
 
Soon, Jaruzelski has adopted proposals for Gorbachev on behalf of Polish. When the case came to Warsaw, Mr Geremek, Michnik, Kuroń and Mazowiecki went in haste to Moscow and almost kneel wybłagali Gorbachev not to do. What kind of influence they used no one knows, in the end, 

Gorbachev przystal on their requests. Consul General in Krakow, p. Serdaczuk was talking about in the presence of Prof. Edward Prus. Also confirmed is the Member of Lithuania to the USSR Jan Ciechanowicz in an interview with Stanislaw Sadowskim from Toronto. It also said the New York press. It was published in the National No 4 (2) (2006).

 Apparently the same Gorbachev did with Kohl by Wrocław and Szczecin during talks about zjednoczenkiu Germany, but Kohl said he would wait for the traffic to the poles. Source: Helmut Kohl said a German journalist Dieter Shmitzke on June 1, 2005 and published in the newspaper "Bayerische Fulle" Nr. 2.

As for 'Kalingrad Oblast' - the northern portion of pre-1945 German East Prussia:

see page 12 at http://www.russian-lawyer.co.uk/Kaliningrad_Integration.pdf

Seemingly, the Society of East Prussia expects a change in the status of Kaliningrad to occur sooner or later. In his address to the 2000 national meeting of the Eastern Prussians, the speaker of the SEP, Wilhelm von Gottberg, pointed out that it will be impossible to preserve the present status of the “Königsberg region” permanently. He gave expression to his hope that someone will take a chance to change its status and that the opportunity will not be lost, as was the case when Gorbachev offered to sell Kaliningrad to Germany and the German government rejected the offer.
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In his later interview “The Königsberg region and its perspectives”18 he even mentioned a concrete purchase price estimated of 48 billion DM. Kohl and Genscher rejected the offer and the major Genscher reason was that he did not want to have “Königsberg as a gift”.

If I recall correctly, I have seen an account of this with Kohl turning down the offer as if it were premature, with words to the effect of East Prussia having to return to Germany under the proper set of circumstances, as if already predetermined.