Is it possible for a 98 pcm to "lose" a tune

Sorry if this is in the wrong section, but as the title states is it possible for the pcm to lose a tune? I had my car tuned last year and it ran awesome for the first day, but literally overnight the shift points dropped from 6700rpm to 5800rpm and the rev limiter dropped from 7200rpm to 6700rpm and the car felt like it lost a lot of power. The only change I made after the tune was I pulled the abs fused as I was advised to do so by the tuner since the car has 26s up front and 28s in the rear. Is there a simple fix for this or do I need to get the car totally retuned?
On a side note just yesterday the car had a PO118 code and I found that the temp sensor and plug is fried.

Thanks in advance

No it cannot. Once the tune is in there its in there.

You set the tune by the window sill too long, Damn neighborhood cats must have got it

check your fuel pressure, shift points dropping and loosing power sounds like low fuel rail pressure, and fuel trims going through the roof.

A tune isn't on top of a stock tune...it's flash memory, and the tune replaces the old numbers with the new ones...they're there until someone replaces them again, OR the memory chips fail...they can't revert back to old numbers though.

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Originally Posted by mbray01

check your fuel pressure, shift points dropping and loosing power sounds like low fuel rail pressure, and fuel trims going through the roof.

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Agreed. Calculations getting all messed up from fuel trims going nuts. Change the fuel filter and make sure the pump is ok. I bet a lot of problems will go away.

Ok I will start with changing out the filter and go from there. Should I check the fuel pressure at the rails? The car has a new racetronix pump with hot wire kit so hopefully I don't need a new pump. Thank you very much I will report back with what happens after I swap the filter

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Originally Posted by Godspeed798

Ok I will start with changing out the filter and go from there. Should I check the fuel pressure at the rails? The car has a new racetronix pump with hot wire kit so hopefully I don't need a new pump. Thank you very much I will report back with what happens after I swap the filter

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Pressure might be too high also...you want to see 58 PSI at the rails.

What would cause high fuel pressure at the rails? Also my plugs look like the car is running lean

Ok I checked the fuel pressure at the rail. When I key the ignition on it reads 50psi when I start the car it's hits 62psi and will stay steady at 62 at all RPMs. The car does not struggle to start or hunt for idle. Why would my fuel preassure be so high? It needs to be at 58psi right

62 isn't really high at all...the difference from that to 58 is minimal.

Changed my fuel filter and burnt ect sensor and its still the same. Would it make a difference that my car was tuned about a 3000ft lower altitude?

Could a bad iat sensor cause these problems? I'm running out of ideas.