Renault traffic van that has no power until turbo starts to boost. Some times when i labour the engine at low revs the glow plug light will come on too? Any idea's?? Thanks

I have one RENAULT TRAFIC
van and has no power when I derive keep going of which I should full stop and start again,I have spend a lot of money to sort out this porblem . so if any one can help me with this sutation it will be great :)

I've got trafic 100dci 2001 year-had poor exceleration upto 2000 revs then turbo cut in,also at speed-mainly uphill the power would start to pulse(like small jerks forward)until it ran out of steam-80ish,changed egr valve-didn't fix it! then tested air flow meter and found figures incorrect,so replaced,also tested the tubo rod(down the back of the engine -visible with air filter housing removed)this was very stiff,so used wd40 to clean then spray oil to lube and worked the rod backward and forward until it moved freely.put all back together and that was it-back to normal-hooray!! have to point out that the van will not rev past 3700 revs when it is loaded-it has a load sensor,unloaded or partly loaded it will rev to I think about 4100 revs(don't quote me on that though) do hope this will help whoever and God bless