Engine Loss Of Compression/power

[Flexus Lexus]

i everyone,

i recently had my car taken to an automatic transmission specialist to have my gear box looked at as it was having trouble changing from 2nd to 3rd :( ........so i thought........in the end i have been told the gear box is fine :D , it reaches all gears manually but there is a significant loss of power in the engine :( , and the timing is all way out.......hence why when its in drive it wont reach the higher gears. so with a good tune and the timing belt fix will this fix my lack of power under load, because my car seems to be revving and idling fine??????

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thanx :D