There is a reason why Imrans away record doesn't look as impressive as his home one and it's this.
Imran as the best bowler and star all rounder in the team was overworked. He bowled more overs per innings than almost any modern pace bowler and on average bowled 22% more deliveries per innings than a McGrath or Walsh. Add his batting and Captaincy on top of that and it's obvious he had a huge workload.
This took a toll on him and it would show in his 4th innings bowling performance. His bowling average in the 4th innings is horrific despite 4th innings pitches typically being more bowler friendly. The vast majority 14 out of 19 of those 4th innings came in away Tests. Here are his bowling averages for away Tests in each innings (I've provided Wasim Akrams away averages for comparison in brackets)
1st match innings 20.52 (27.10)
2nd match innings 29.37 (26.72)
3rd match innings 21.11 (21.31)
4th match innings 48.50 (21.63)
Now you can see why his overall bowling average in away Tests doesn't look quite as impressive.